- "Thou shall only slay by thine oath, and serve by no other. Hold sacred the Blood most Vile, for it is thy eternal blessing."
- —A rare excerpt of Oath of the Sacred Blood, recorded by late Inquisitorial Acolyte Bram Rekeah
A crimson specter within the tumultuous River of Exiles, the Vile Blood is a force even the most stalwart of traitors implicitly fear. Striking seemingly at random and leaving nought but utter bloody ruin in their wake, these monstrous devotees of Khorne have terrified the Exile Sector and Imperium at large since their first official appearance in the final year of the 34th Millennium, known today as the Great Massacre of Arcadia V. However, attacks fitting their modus operandi have been common within the Exile Sector since 236.M34 if Inquisitorial records are to be believed.
The Vile Blood stand apart from their fellow traitors and brigands in several conspicuous ways, each of which has worked to cement their bloody legend within the minds of the peoples of both the River of Exiles and the greater Imperium. For the Vile Blood are no middling berzerkers, no mere madmen. To many within the Exile Sector, the Vile Blood are horror all their own.
Of their many strange traits, most conspicuous is the sheer monstrous extent to which some of their number have been shaped and twisted by the fell energies of the Warp. So mutated are the Vile Blood that upon their first official contact with Imperial forces upon the world of Arcadia V, that Guard units were reportedly unsure if the enemy were Daemons or Xenos, and it was only after close inspection that they discovered to their horror that these beings were once human in shape. The Vile Blood bear into battle, not only blades and boltguns, but also savage rending claws and sword-like limbs. Great bladed talons, scaly hides, and chitinous exoskeletons fuse with fleshmetal Power Armor to create a visage terrible to behold for even the most stout hearted man. Almost all semblance of the holy form of the Astartes has been lost, having been claimed by mutation and trophies of war. So horrible and prevalent is this monstrous visage that many agents of the Inquisition and heretical mystics theorize that the Vile Blood are either all possessed by daemons or that they are subject to some powerful Warp-Curse (or blessing, depending on the perspective).
But their shape is not the only terrifying aspect of the Vile Blood, merely the most outward. Having taken the black blood oaths of Khorne, these monsters in the mocking shape of Astartes bring terror inducing phenomena in their relentless wake. Days before their invasions, soon to be besieged worlds report conspicuous astral phenomena, great Blood Moons wreathed in writhing red auroras. When the Vile Blood themselves finally arrive, realspace seems to almost rebel at their mere presence, a haze appearing about them that seems to damage surveillance equipment.
But most peculiar is this Warbands uncharacteristic behavior. As opposed to what would be expect of such inhuman monsters dedicated to the bloody god of slaughter, the Vile Blood are hardly slathering, blood drunk berzerkers. Noted to hold themselves to a strict warrior code of honor and fair conflict, known as the Oath of Blood most Vile, a chivalric code of conduct that espouses fanatical values of martial honor and various battle rituals. Though the Vile Blood do indulge in more bestial practices such as the consumption of their foes flesh and bathing in their blood, they are known for strange practices that defy their horrific shapes and bloody creed. The Vile Blood have never been documented to directly kill civilian targets, and they abhor the use of underhanded tactics and torture. However, while they see such things below them, they do not often restrain their mortal followers, their Men at Arms, from such horrific acts in the name of the Blood God. Further adding to this dichotomy, the Vile Blood commonly speak in an archaic dialect of High Gothic, a diabolic tongue that only the more cultured and educated citizenry of the Imperium can understand. However, should a lowly "Peasant" earn the dubious honor of dueling a member of the Vile Blood in single combat, he will be addressed in a rather elaborate dialect of Low Gothic.
The Red Specter
In the year 236.M34, contact with the lone Imperial Guard outpost on the Dead World of Argentum was lost. A meager garrison guarding a Munitorum ammo depot, its loss was noted only after several years of neglect. While the loss was certainly unusual, its proximity to the River of Exiles left little to the imagination as to the fate of the garrison and their cargo. Forward Imperial Guard forces were deployed to recapture the garrison. Though relatively small the fortress depot was well defended, and the world itself was of very minor strategic value, thus it was initially assumed to be the work of raiders or pirates. However, the nature of the assailants proved to be far greater. First and foremost was the lack of signs of a struggle at the outer wall of the fortress depot, the gunners had never even fired a shot from their turrets upon the parapets. There were signs of heavy fighting within the outpost however, a horrific melee had ensued, with the defenders being utterly slaughtered within the confines of their fortress. Several areas showed valiant attempts at a last stand, though such attempts seemed to end in total annihilation as the unknown assailants closed in and tore the defenders limb from limb. Those that scattered to the various warehouses fared no better, run down and hewed to pieces by talons and blades. The pict-captures and security holos were heavily corrupted, assumed to be due to a lack of maintenance or a recent Warp Flare from the River. It was the nature of these killings that later warranted Inquisitorial investigation, for the apparent speed and savagery with which the garrison was dispatched bespoke of something greater than the average pirate rabble.
Though Argentum was eventually forgotten by most, it soon became apparent that several more such incidents had occurred as outposts throughout the River perimeter went dark. Each was revealed later to have been destroyed in the same manner, with the enemy bypassing the outer defenses and leaving no survivors in the resulting melee. In spite of this, only two Inquisitors continued to track the assaults, with the rest of their contemporaries assuming the massacres to be unconnected or citing graver threats that called for urgent attention. For several centuries the mysterious massacres continued, and the two Inquisitors, Buford Nix of Ordo Hereticus and Codimus Chen of Ordo Malleus, joined forces to find the culprits. Slowly but surely witnesses began to arise as the assaults grew in size, from measly outposts to sizable frontier settlements and large garrisons waiting to be moved to the front. Though the specific nature of the enemy remained unsure due to the state of most survivors, a pattern of attack was noted. These "Crimson Beasts" had yet to attack any sizable civilian population, opting for military outposts or worlds with a large Imperial Guard presence. Though clearly daemonic in nature, the attackers seemed to spare unarmed targets, often leaving personnel such as cooks and communications officers alive. (though the cultist units that followed in the monsters' wake were eager to train their weapons on non-combatants) Their human followers were reportedly well trained and disciplined, though they came only in support of their masters, and rarely engaged in direct combat during the smaller raids.
The duo of Inquisitors would continue to tack their quarry throughout the eastern expanse of the Exile Sector, years of investigation, following the steady trail of murder and violence.
While information on the Vile Blood is sealed by all but the highest Imperial authorities due to the daemonic nature of the Warband, even the Inquisition admits it knows much less than it would like about the inner workings of the Vile Blood. Most samples of Gene-Seed captured by Imperial authorities is so mutated and twisted that to definitively identify the linage that the Vile Blood hail from is all but impossible.
Most simply assume off hand that the Vile Blood were formerly Blood Angels Successors, citing their hunger for human flesh and hyper-aggressive combat doctrine. Some even dare to theorize that they are descended from the ranks of the Scarlet Serpents, but such accusations are usually put down due to the sheer amount of respect the Chapter has accrued in its old age, and the scarlet ones themselves remain mute on the subject. However, no Vile Blood encountered in the field of battle have shown the mad berzerker fury they should have if they had inherited the Blood Angel's horrible dual curses, as all members of the Vile Blood seem to be completely lucid.
Inquisitorial authorities have also cited certain genetic sequences within what little Gene-Seed there is for study that are very similar to those sequences found in Dark Angels Astartes. This, combined with the knightly rituals and behaviors of the Vile Blood, have led some, even those few privy to this information within the Unforgiven, to suspect that the Vile Blood may very well be lost Sons of the Lion. Supporting this information are the records from the Battle of Datis, in which the Vile Blood specifically targeted the homeworld of the Lightbringers Chapter in an attempt to raid the Dias' Gene-Seed banks. It is likely that a Warband so obsessed with personal legacy would seek out Gene-Seed that shares their linage.
While extensive mutation makes an exact approximation on genetically ingrained habits within the Vile Blood all but impossible, field observes have noted several behavioral habits that the Vile Blood as a whole share. First and foremost members of the Vile Blood are noted as naturally superstitious, taking great confidence in perceived omens and lucky symbols. Thus they regularly decorate their hideous forms with various icons and trophies, in an attempt to ward off misfortune on the battlefield. Vile Blood are also considered to be remarkably sensitive to idols and icons of the Imperial Cult, having been reported to shy away from consecrated sites and even recoil at the sight of the traditional Aquilla hand gesture done by faithful Imperial citizens. Unfortunately this has led to some assuming that such icons can harm or permanently ward off the Vile Blood, when in fact the discomfort is mild and likely, temporary. It is likely that, considering the Vile Bloods superstitious instincts, that they consider holy Imperial signs as bad omens, and thus wish to avoid them for fear of being "tainted" with the bad luck these symbols of the enemy hold.
The Vile Blood are fearsome warriors, armed with great and terrible weapons of war. Though armed with the standard fare of lethal weapons crafted for the hands of Astartes such as the Bolter and Chainsword, the Vile Blood are known more for their horrific mutations and ravenous Daemon Weapons. Much of their wargear has been so twisted and corrupted by the energies of the Warp that it has often taken on a small measure of the power of Chaos, making the Vile Blood all the more potent in battle.
The Vile Blood's mortal followers, their Men at Arms, are noted to be outfitted with a potent array of weapons, armor, and materiel. This puts them on the level of most rank and file Imperial Guard Regiments, though their daemonic blessings and fanatical Blood Cult makes them twice as fearsome. The Men at Arms are noted as disciplined and competent soldiery, not a mindless cultist rabble, and have been a force to be reckoned with even without the direct support of their monstrous overlords.
The Vile Blood strike suddenly and with ferocious potency, their fleets materializing through a red nebula that heralds their assault. The initial fleet battle over a planets surface is usually a relentless advance, the longer range weaponry of the fleet pounding defensive lines of enemy vessels before launching the blood hungry boarding parties.
Once the path is clear to the unfortunate planet's surface, the forces of the Vile Blood deploy immediately via drop pods. This first wave is notably made up mostly of Raptors, Possessed Chaos Marines, and Bike Squads supported by light infantry elements of the Men at Arms, and is meant to secure a foothold for further deployments. The second wave is of the more rank and file forces of the Vile Blood, supported by the heavier elements of the Men at Arms. The Vile Blood prefer combined arms, forming a vanguard for their mortal followers but notably hanging back if their support is lagging, their caviler manners not utterly eclipsing a modicum of tactical sense.
The Vile Blood place an emphasis on the sheer relentlessness of their assault, giving the foe no respite in a sweeping advance. Such a relentless advance is made possible by the Vile Blood's ability to close and utterly ruin the foe in close quarters combat, rapidly circumventing all barriers and concentrations of ranged weapons. However, the Vile Blood have been noted to make certain engagements sporting or more spectacular, holding if the enemy looks unprepared for a proper battle and amassing more forces at these stalling points to further add to the scale for the glorious battle to come.
Should the Vile Blood encounter a foe too firmly entrenched to be assaulted directly, they resort to their infamous Warp Talons and elite light infantry forces to smoke out the enemy and engage them in direct combat. It has been noted in the past that the Vile Blood can be easily led into an ambush, but usually at the cost of a force to be used as bait as nothing but combat will entice them. And while the Vile Blood themselves are ill-suited to a drawn out siege, their Men at Arms are more than capable of waging such wars of attrition.
The Vile Blood abhor dishonorable tactics, eschewing spies and assassination for glorious battle and honest respect for foes willing to do battle on the open field. Ambush is often considered an underhanded maneuver, fit only for the near mindless Warp Talons and desperate peasants. Sabotaging the enemy's supply lines outside of a siege scenario is seen as counter productive, for by depriving the enemy of their means to fight is also depriving the Vile Blood of the honorable combat they so seek. Some Vile Blood relish in fighting a foe who utilizes such tactics, considering it a worthy challenge, and often treat being ambushed as a form of sport.
As accurate reports on the actual strength of the Vile Blood's numbers are unavailable, one can only assume that the Vile Blood operate in a manner akin to the standard Codex Astartes layout, though reference to a unit beyond average Squad size has yet to be made in any intercepted vox leads some to infer that the Vile Blood operate solely on a squad by squad basis, with no greater officer core save the Blade Lord and his intimidate staff. This would explain the somewhat disjointed nature of the Vile Blood's sweeping advance, as each individual unit of Astartes seems to take its own initiative. However, some greater command structure does seem to exist, though whether that is more a result of individual groupings of Vile Blood making accurate assessments of their tactical situation and working in concert or the overreaching command of the Bade Lord himself remains uncertain.
Meanwhile the Men at Arms are noted to follow a strictly regimented and clear hierarchy based on seniority and personal combat ability. Intercepted vox communications show that the Men at Arms are given quite a bit of freedom by their masters, the Vile Blood trusting their more experienced minions to make competent decisions based on the battlefield situation. Generally speaking the Men at Arms modus operandi seems to be the continuous support of Chaos Marine squads with armor and artillery as well as maintaining supply lines and clearing out pockets of resistance that have survived the Vile Blood's rampage. At the head of the Men at Arms is the so called Master of Arms, a rank equivalent to an Imperial Guard Colonel. Unlike most mortal followers of the Chaos Marines, it seems that the Master of Arms is a high ranking warrior within the Vile Blood's hierarchy, seen as a direct member of the Blade Lord's command staff equivalent to his other Chaos Marine retainers, though whether he actually outranks individual Chaos Marines is unknown. As the Master of Arms is hand picked by the Blade Lord himself on prowess of arms and command, it is likely that the respect such a man or woman receives from even these inhuman warlords is well deserved.
Known within the warband's ranks as the Dread Fleet of Crimshour, the warfleet of the Vile Blood is dreaded across the whole of the Exile Sector. Composed of Astartes-Pattern Strike Cruisers and several variants of commonly Chaos aligned Cruisers, the Dread Fleet of Crimshour is arrayed in such a manner that the lance batteries of the more rank and file Chaos vessels can lay down a withering support barrage from a distance while the Astartes warships launch themselves headfirst into the foe, disgorging vast amounts of macro canon and plasma battery fire while also unleashing hordes of boarding craft.
The flagship of the Warband is the Battle Barge known as the Crimson Omen. A monstrous vessel bedecked with the bladed iconography of Khorne, the Crimson Omen is a harbinger of doom so feared that Imperial Captains have been known to face the Bolt Pistol of the Commissar rather than dare to brave its infamous plasma batteries and fusillades of boarding vessels.
The Cavilers of Crimshour
- "Mine is a steed of brass and Blood, anointed in the Skull King's most sacred of ways. Verily, there hast been no steed to rival her mighty roaring heart nore match her robust greatness upon the sacred field of war. She is mine steed, and I am her master, and together we will bring forth the blessings of the Blood most Vile."
- —The Caviler Oath
Considered the elite vanguard of the Vile Blood's murderous assaults, the Cavilers of Crimshour are several squadrons of Chaos Space Marine Bikers. Each of these bands of eight riders are said to be most blessed by the touch of the so called "Blood most Vile", and are thus imbued with warrior might and marital prowess far and beyond any other member of the warband. At their head is the mighty Blade Lord himself Aluduan, riding forth at the head of his fearsome honor guard of chosen berzerkers.
Their warbikes are imbued with daemonic essence and sanctified in profane Khornate ritual, giving them strange powers beyond that of a typical warbike. The Cavilers are noted to be able to phase in and out of realspace at a whim, becoming ethereal as a daemon might in order to pass through enemy fire and obstacles. In this manner they become truly relentless, certain to close into close combat with the enemy and wreak bloody havoc.
The most prestigous of the Cavilers, known as the Blood Dragoons, form Lord Aluduan's personal bodyguard and command staff. Each Assault Bike of the Blood Dragoons bears the personal heraldry of its master branded upon its brass hide, further distinguishing these elite warriors from their already prime contemporaries within the Cavilers of Crimshour.
The Crimson Lance
- "We art the tip of the spear, the hook of the claw, the edge of the axe. Should thine enemy be possessed of uncanny resolve and of great fortitude, then call upon us, the Lances of the Skull King, that he may render judgment of their valor."
- —The Oath of the Lance
An elite triplet of of Khornate Terminator Squads, the Crimson Lance is the Vile Blood's most potent heavy assault force, a dauntless juggernaut capable of reducing even the most mighty of foes to bloody ruin. They stride into battle, armed with their signature Crimshour Murderglaives, great roaring Chainglaives designed to rip and rend through all but the finest armor. Their pattern of Terminator Armor is uniformly the archaic Saturnine Pattern, an esoteric model functionally identical to the Tartaros and Indomitus designs, this armor's one advantage is the hard-point located on the back of the suit, allowing the Crimson Lance to wade into battle with an off hand heavy weapon mounted between the suits massive pauldrons. This design benefits their use of their massive two handed melee weapon, though members of the Crimson Lance are known for entering battle outfitted with Legion Chainfists, Lighting Claws, and massive one-handed Chain Weapons if their engagement range is too tight to utilize their signature weapon.
The Crimson Lance are infamous for their undefeated status and their reputation in boarding actions and direct assaults, having utterly slaughtered all but the most capable opponents that have crossed their path. At their head is the infamous Rhudkaiser, the Bulwark, whose exploits are legendary. Rhudkaiser's greatest claim to fame are his actions at the so-called Great Massacre of Aracdia V, where he allegedly slew the famous Lord Inquisitor Buford Nix of Ordo Hereticus in single combat.
Hounds of the Skull King
- "Let slip the hounds of war, that our enemy may know no solace from glorious combat!"
- —The Blade Lord's decree during the infamous Burning of Talspho Fields
The most distinguished unit of Warp Talons within the host of the Vile Blood, the Hounds of the Skull Kings are the most prized hunters of the Blade Lord Aluduan. As the warband tends to treat their many Warp Talons as little more than hunting beasts for clearing out boarded starships, fixing enemy forces in place, or running down routing foes, for a single unit of them to gain such a vaunted reputation is a rare thing indeed. The Hounds of the Skull King are marked by their distinctive collection of skulls, their armored forms absolutely covered in the innumerable trophies of war to the point where their armor is almost totally obscured by the adamantium dipped bones of the fallen.
The Hounds of the Skull King are only dispatched upon Aluduan's decree, usually to hunt down those who refuse to engage in glorious combat such as Eldar or more skirmish oriented armies of the Imperial Guard. The relentless claws of the Hounds of the Skull King have yet to fail their master in securing their prey, and are capable of such feats of raw butchery that their reputation is subject of awe even amongst other Traitor Marines of the River. At the head of the pack is the beast known only as Draco, a diminutive but nonetheless horrific specimen of the Warp Talons. Though notably shorter than the average Astartes, Draco is allegedly so swift and capable with his massive mutant Lighting Claws that even Dark Eldar Wyches have been seen to struggle against this Warp cursed monstrosity.
Absalon the Indefatigable
- "Hail to thee, Axeman of Khorne! Hail to thee, great Wallbreaker, mighty Tankslayer! We shalt follow ye, Absalon the Indefatigable, into the teeth of the enemy, for the great Skull King, for the Blood most Vile!"
- —Knight-Brother William at the Fall of Tagodon
A fearsome Kytan Daemon Engine, Absalon the Indefatigable is a murderous war machine that serves as the battering ram of the Vile Blood, created for the sole purpose of hunting down and butchering both armored convoys and smashing down fortifications. The Knight sized Daemon Engine is loosed into battle, a living avatar of the Blood God's eternal and unrelenting fury as the murderous resilience of the Machine is combined with the rage of a daemon.
Absalon has long been a key weapon in the Warband's vast arsenal of daemonic tools and heretek weapons, chained upon his brass throne upon the Shade of War until such a time as it is needed on the field of war. When unleashed, Absalon is often followed by a fanatical cadre of Berzerkers, who see him as a hereald of Khorne himself on the battlefield, and consider to fight in his shadow a deeply religious experience. Absalon is an ancient engine of war whose might his the stuff of legend and nightmare in equal measure, having felled Imperial Knights, Greater Daemons, Xenos monstrosities, and even a Warhound Scout Titan in its long eons of battle and bood.
- "Mine eternal liege, I pray unto thee, watch over our conduct on this, your most holy of days. For as Analise, the Honored First Blood Saint hath ordained in your year of M33, this shalt be a day of righteous victory! I pray unto thee, almighty Skull King, resplendent upon the Throne of Brass and Blood, look upon our works and find them worthy!"
- —Knight-Brother Davion Kell leads his Battle-Brothers in unholy prayer before an altar of skulls during the Kojphosian Genocide
A distinct code of chivarlic conduct and honor bound oaths combine to make the average Knight-Brother of the Vile Blood a beast quite unlike his fellow devotees of Khorne, producing a well spoken and disciplined warrior of the so-called Skull King. In spite of their savage ability in close combat and their unholy visage, the Vile Blood are almost regal in their poise, refusing to bloody their claws on the bodies of the innocent or infirm. Though heavily suppressed or spun by Imperial propaganda, tales of the Vile Blood releasing prisoners of war after a conflict and sparing the lives of the wounded and dying are just as widely circulated as the tales of bloody savagery and utter inhuman barbarism they display when the enemy is in their grasp.
No member of the Vile Blood would dare harm a civilian willingly, and it is believed that doing so would so mark the transgressor so severely that he would be subject to corporal punishment and then cast out from the Warband, stripped of all rank, title, and even name. The taboo is less harsh, but does extend to the slaying of the infirm or grievously wounded should they desperately stand against the Vile Blood, as it is seen as unsportsmanlike.
Also at odds with their devotion to the god of rage and fury, the Vile Blood are markedly well mannered and slow to anger, though this does vary between individuals to an extent. Broadly speaking, while the Vile Blood relish in combat, they tend to treat it as a great religious sport, a game in which their foe is an equal participant. It seems to escape much of the Vile Blood that their enemies are fighting for their lives, and do not wish to die in battle, no matter how glorious the carnage may be.
The Vile Blood are fond of omens and symbols, prone to various esoteric and mainstream superstitions regarding the fates. Some Vile Blood take this to the extreme, taking every unusual coincidence or fitting symbolism as a sign that they must ruminate upon before prosecuting any other duty. This can be tedious if said omen appeared mid-battle, as the Knight-Brother will stand in contemplation of the subject of his attention, killing only those who interrupt his introspection, until he is satisfied with an answer. Likewise, they avoid Imperial religious iconography and places of holy value, believing that such places and symbols hold a measure of bad luck or a power to curse their fortunes in war. Indeed this superstition can easily be said to be the one thing the Vile Blood may react to in a manner akin to fear, though if pressed they will not be held back by church walls and Aquilla pendants for more than a passing moment.
However, the Vile Blood's Men at Arms are much more the archetypal Khornates, ruthlessly disciplined, blood hungry madmen who seek only to slaughter and kill in the name of the Skull King. The Vile Blood seem to allow this only to an extent, as the mass execution of civilians by the hands of their Men at Arms, while considered unavoidable due to the fallible nature of mortal men, is inexcusable when there still remains a foe to bloody one's blade against. Thus, while the Men at Arms may rampage with impunity, it is only when their masters can see no better use for them. To catch their minions raping and pillaging when battle is still yet to be joined is enough to warrant the wrath of the Vile Blood, which they will vent with alarming speed.
The Great Massacre of Arcadia V
The Munique Massacre
The Uldrian Carnage
The Hellraids of the Tanit System
The Kojphosian Genocide
The War for Magniar Prime
The Second Exile Wars
- "Ah! The beastie comes honored brothers! I say unto thee, Warboss Grimgutz, have at thee!"
- —Knight-Brother Daultian
- "Its almost humorous, we are loyal to our oaths, and our foes and allies call us dishonourable for how we conduct war. They are mutated and corrupt servants of chaos, and the way they conduct war is considered 'honourable'."
- —Idria Salaman, Obsidian Blades 2nd Captain
- "Ok, children, slow down there a little. If you think you can "cleanse" me then you really have your work cut out for you. It's not as easy as one might think. I've been a little less than clean since before you were born."
- —Calios Kottel, Lord of the Void Sirens
- "God-Emperor save us! Send reinforcements now! Feth they've broken through the walls!"
- —Syprios Militiaman's final broadcast
- "Cross blades as warriors? You jest surely. You are nothing, just a beast to be put down. Die."
- —Wings of Salvaxes Assault Marine facing off against a Vile Blood warrior.
- "If it was anyone else, I wouldn't even consider a curse of our dishonourable names. Get the sniper's ready, just in case."
- —A Star Reapers Nui-ta called to a challenge
- "Did he just yell 'I challenge thee'?"
- —A somewhat befuddled White Lions Sergeant
- "Look at you, Traitor. Corrupted. Nay! Defiled! Beyond any hope of recognition! And yet, you dare to pretend that you have some semblance of honour? Very well. I shall teach you that honour rests with the ashes of the Betrayed, on the black sands..."
- —Void Lord Valien Torin at the onset of the Uldrian Carnage
- "Please tell me I don't have to sit next to these guys on the ship."
- —Dolfdir of the Crusaders Once Crossed before the Nerio Invasion