Acheron is an eternal battlefield of endless conflict. It is a plane of law where conformity takes precedence over any thoughts of good. Unending battles take place across the entire plane between huge armies, with no chance of victory or cease-fire. Each layer of plane consists of a huge numbers of iron cubes of varying size, from continent-sized to small islands; not all of these are actually cube-shaped, but they are generally called cubes nonetheless The cubes float in an air-filled, infinite space, occasionally colliding with each other.

Every cube face is habitable, with gravity always being directed towards the cube's center; furthermore, the cubes are filled with caverns and tunnels. The cubes that make up each of the four layers of Acheron are pitted and scarred with cracks and dents from their many collisions and craters from their many battles. On the orderly plane of Acheron, the cubes always rust or fracture along straight lines and at right angles. Some of the cubes are only a few hundred feet on a side, but others are big enough for whole cities and kingdoms. Geometric shapes other than cubes exist, though they are rare (except on Tintibulus, the third layer). Vision is normal on Acheron. The plane is lighted by a gray, fluctuating illumination that varies slightly between bright moonlight and a dark, cloudy day. Hearing is also normal, though the echo of colliding cubes and the ring of battle is always in the background.

The light on Acheron varies between that similar to bright moonlight to that of a dark and cloudy day. The sound of battle resonates around the plane and can always be heard in the distance.


As with other outer planes, Acheron is spatially infinite, consisting of four infinite layers or sub-planes. Acheron's first layer, Avalas, shares borders with the neighbouring planes of the Nine Hells of Baator and the Clockwork Nirvana of Mechanus; travel is possible between Acheron and these planes at certain locations.

Acheron has the following traits-

  • Objective Directional Gravity: The strength of gravity is the same as on the Material Plane, but which way is down depends on which face of the cube you're on. Walking across edges between faces can be dizzying for the inexperienced.
  • Normal Time.
  • Infinite Size: Each cube is finite, but the void the cubes hang in is infinite.
  • Divinely Morphic: Acheron changes at the whim of its deities. Ordinary creatures must use spells and physical effort to change the infernal battlefield.
  • No Elemental or Energy Traits.
  • Mildly Law-Aligned: Chaotic characters suffer a –2 penalty on all Charisma-based checks.
  • Normal Magic.


Portals to the Outlands, Mechanus or Baator are often the rims of the gravity wells that the blocks orbit. The unholy River Styx has a source on Avalas, on the block called Wreychtmirk.

The River Styx although occasionally it'll flow through channels or tunnels - it defies gravity and plummets from cube to cube, sometimes sliding across a cube's face in vast sheets and drowning entire armies, raining down unexpectedly as the cubes shift, and eventually somehow falling between layers to end up as frozen shards of ice in Ocanthus.


Renegade armies filled with every sort of creature wander the faces of Acheron looking for enemy forces to fight. However, mutiny or madness soon brings down even the strongest military leader, leaving most armies without a true objective other than the destruction of other renegade armies. Sometimes armies of undead or constructs last longer, because they are able to mindlessly fulfill their last orders. Armies that have not gone completely mad may still seek a goal, such as the defense of a realm, the procurement of provisions, the overthrow of an impostor king, or any of a hundred other causes. Unfortunately, because most of those causes were important on a plane far from Acheron, even the most steadfast armies soon lose focus and go renegade. Achaierai, devils, imps, fomorians, rakshasas, dragons, and yugoloths also inhabit Acheron. Rakshasa clans rule several hidden cubes throughout Acheron, all cloaked by powerful illusions. Clockwork creatures from Mechanus keep a few hidden mining colonies scattered through the two lowest layers of Acheron.

Finally, Acheron holds enormous flocks of birds. Ravens, vultures, gulls, bloodhawks, and swallows tumble on the wind, sated on the carnage of the many battlefields.


Acheron has four known layers:


The first layer of Acheron, Avalas, is also called The Battlefield. It contains the highest density of metal cubes and is thus host to the most fighting on the plane. The cubes are dotted with fortresses and covered with battlefields. Collisions between the cubes causes them to break apart in to smaller cubes, hence the smallest cubes are the oldest on the layer.


The realm of Nishrek is located on Avalas. It is home to the orc deity Gruumsh and the other deities of the orc pantheon including Bahgtru, Ilneval, and Luthic.

Bralm's realm, the Hive Fortress, is in Avalas.

The citadel of Scourgehold is the realm of Hextor, the god of tyranny and half-brother of Heironeous. Here Hextor presides over his legions as they train in The Great Coliseum.

Clangor, is located here. It is the realm of goblin deities Maglubiyet, Khurgorbaeyag, and Nomog-Geaya. Avalas also contains the realms of Amatsu-Mikaboshi (The Brilliant Land) and Lei Kung (Resounding Thunder).

With the destruction of Iyachtu Xvim, Bane has returned to his Black Bastion, a massive fortress-castle on the layer.

Known CubesEdit


  • Arena of Bloo'dveeri
  • Vorkeham ("the City of Fumes") The "Mercykillers" philosophic sect, which believes in the enforcement of absolute justice without regard to collateral damage, has its headquarters here. ("You broke the law, now you're gonna pay.") Their home city is made of titanium with acid fountains. Check vs. constitution each day or remain in bed with the dry heaves. Mercykillers are immune.

Avalas is the spiritual home of the most dedicated race-supremacists, and all who wilfully forgot their good causes in the excitement of battle. The Army of Purity has its headquarters here. This is a common location for the headquarters of sects devoted to vengeance and war.


The universal junkyard of battle, where all the garbage of war finds its way and turns to stone. Each block is hollow, a shell a few miles thick. Inside is junk. Compared to Avalas, Thuldanin has a relatively small population. Geographically it is very much like the first, consisting of numerous huge cubes. On this layer the cubes are scarred and pitted by battle. Many pits lead down to labyrinths containing the refuse of the endless battles of the plane. The remains of broken war machines and other devices line the interiors of the cubes, even some finely crafted weapons can be found amongst the rubble.

Thuldanin has a preservative quality that results in the petrification of objects and creatures that spend too long on the layer; savvy visitors spend no longer than 29 days here.


The realm of Hammergrim, a separate plane in the 3rd-Edition Forgotten Realms cosmology is located on Thuldanin. It is the realm of the duergar god, Laduguer.


The mines of Marsellin are the richest source of treasure, and they are guarded by a huge rust dragon who has joined the Mercykillers.


Tintibulus contains a large number of four-sided, five-sided, eight-sided, and other solids in preference to the six-sided cubes that predominate the other layers. A layer of thick dust coats the surface of the solids here, which are made of a grey volcanic stone. Magicians' libraries are scattered here, and is the best place in the Multiverse for magical research.


The fourth layer contains no regular shapes, but many shard-like solids of black ice with razor sharp edges. The shards fly about in violent motion, referred to as a bladestorm.

At the extreme of Ocanthus lies the Cabal Macabre, the realm of the goddess of death and magic, Wee Jas. Her domain takes the form of a huge and intricately carved ice castle, that glows with a pale light. Wee Jas' powers quell the bladestorm within a half mile of her location, allowing her to maintain her realm. Cabal Macabre is located on a huge, possibly infinite shard of black ice which may be a barrier between Ocanthus and a deeper level of Acheron.


  • Achaierai
  • Chronotyryn
  • Rust dragon
  • Steel Predator
  • Bonespear
  • Maug

Spell alterations in AcheronEdit

For every spell, an opposite effect flies off in the form of a crystal. Except for deaths, the effects can be reversed by the touch of this crystal. The crystal lasts one hour per level of the spell, then discharges. Conjured and summoned creatures must obey the letter of any command, but cannot disobey, and a hostage person must be provided in exchange to trade places. The hostage is entitled to a saving throw to avoid the effect, and if this succeeds, the caster must save or become the hostage. If both save, the spell fails. Divination cannot spy on an enemy army. A bad omen, if obtained, will extend the bad luck to the questioner's entire group or army. Spell keys might be able to avoid this. Necromancy used against a stronger target rebounds, and drains two points per spell level from the caster. A spell key might prevent this. Wild mages lose two levels, and no surge is possible. Earth magic cannot affect the iron bricks, fire heats them, and water rusts them.

Wizardly spell keys are rigidly-defined but otherwise meaningless words, motions, and substances. Power keys for clergy are rare.

  • The suggested color for pools from the astral is flame. Ethereal curtains might be metallic red.
  • The dead are immune to electricity and sound, and as an additional ability have various morale bonuses against charm and fear and +1 on attack and damage when in the military.
  • The plane is "mildly lawful-aligned". Chaotic creatures have -2 on charisma checks.
  • -1 on all charimsa checks for all good creatures
  • -1 on all intelligence, wisdom, and charisma checks for all non-lawful, non-chaotic creatures
  • -2 on all intelligence, wisdom, and charisma checks for all chaotic creatures
  • Good-based spells (non-chaotic) require a Spellcraft check (DC 15) for success.
  • Evil-based spells (non-chaotic) work as if caster were 2 levels higher.
  • Law-based spells work as if caster were 4 levels higher.
  • Chaos-based spells simply fail.