Yssian, the Abyssal Engine

Gargantuan undead, neutral evil

Armor Class 20 (natural armor)
Hit Points 583 (35d20 + 216)
Speed 50 ft., fly 40 ft.

26 (+8) 12 (+1) 23 (+6) 17 (+3) 16 (+3) 24 (+7)

Saving Throws Constitution+13, Wisdom+10
Skills Arcana +10, Insight +10, Intimidation +14, Perception +10
Damage Resistances acid, cold, fire, lightning, poison, thunder
Damage Immunities necrotic
Condition Immunities charmed, frightened, paralyzed, petrified, poisoned
Senses darkvision 600 ft., passive Perception 20
Languages Abyssal, Celestial, Common, Infernal (can’t speak); telepathy 100 ft.
Challenge 21 (33,000 XP)

Special Traits

  • Colossal Creature. Kaiju are creatures far larger than the scale of others. Conventional weapons, even highly-enchanted ones, lack the mass to deal serious wounds to a kaiju. The same is true for all but the mightiest spells. When a creature of Huge size or smaller deals damage to a kaiju with a weapon or feature, or with a spell of 8th level or lower, it deals half damage, which can be reduced further by resistance or saving throws. Siege weapons and creatures with the Siege Monster trait are treated like Gargantuan creatures. Gargantuan creatures and 9th-level spells (including lower-level spells cast with 9th-level slots) deal normal damage, which can be reduced further by resistance or saving throws. Kaiju deal double damage to objects and structures. They ignore normal difficult terrain, and treat thick forests, settlements, or mountains as difficult rather than impassable terrain.
  • Legendary Resistance (3/Day). If Yssian, the Abyssal Engine fails a saving throw, it can choose to succeed instead.
  • Spell Deflection. When Yssian, the Abyssal Engine has at least one soul absorbed into its body and fails a saving throw against banishment, confusion, detect thoughts, dispel evil and good, dominate person, fear, geas, hypnotic pattern, imprisonment, magic jar, maze, suggestion, or anything that imposes the charmed condition, it can choose to have the spell target an absorbed soul instead. The spellcaster makes a special spell attack against Yssian, the Abyssal Engine. On a success, one soul is freed from Yssian, the Abyssal Engine’s body, and can be restored to life as normal.
  • Turning Defiance. Yssian, the Abyssal Engine has advantage on saving throws against effects that turn undead.
  • Essence. At the start of an encounter, Yssian, the Abyssal Engine usually has 10 (3d4 + 3) Essence available. As an action, it can spend Essence to cast any necromancy spell. Its spellcasting ability is Charisma (spell save DC 22). It is a 20th-level spellcaster.
Spell Slot Level Essence
1st 2
2nd 3
3rd 5
4th 6
5th 7
6th 9
7th 10
8th 11
9th 12


  • Multiattack. Yssian, the Abyssal Engine makes one or two claw attacks and casts any one necromancy cantrip.
  • Claw. Melee Weapon Attack: +15 to hit, reach 20 ft., one target. Hit: 35 (6d8 + 8) slashing damage, and the target must make a DC 17 Constitution saving throw. On a failure, the target suffers one level of exhaustion.
  • Devour Soul. One creature within 20 feet of Yssian, must make a DC 17 Constitution saving throw. On a failure, it suffers 61 (7d8 + 30) necrotic damage, or half as much on a success. If this reduces the target to 0 hit points, its soul is absorbed into the body of Yssian. The creature cannot be brought back to life until its soul is released by the death of Yssian or through the Spell Deflection trait. Yssian can hold up to five souls at a time.

Legendary Actions

Yssian, the Abyssal Engine can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature’s turn. Yssian, the Abyssal Engine regains spent legendary actions at the start of its turn.

  • Claw. Yssian, the Abyssal Engine makes one claw attack.
  • Spellcasting. Yssian, the Abyssal Engine expends Essence to cast one necromancy spell.
  • Recover. Yssian, the Abyssal Engine regains 75 hit points. Once it uses this ability, it cannot do so again until the end of its next turn.


Yssian, the Abyssal Engine is a single undead horror constructed of the bones and souls of countless individuals. When it comes to the Material Plane, it leaves behind a swath of destruction, consuming soul after soul to fuel ever greater necromantic magic.

Enforcer of Death’s Edicts. What the gods of Death or the Fates decree, none may gainsay. Those who struggle against these decrees may find victory for a time through magic, guile, or force of arms, but when all other options fail, Yssian, the Abyssal Engine is sent to the Material Plane, and it does not fail. According to at least one legend, one who defeated Yssian, the Abyssal Engine would be greater than any power of Death itself, and would assume Death’s place.

Soul Prison. Yssian, the Abyssal Engine slays the living and grows stronger, capturing their fleeing souls. Its captives cannot be restored to life, and only its destruction or a very specific set of circumstances can free one of those captives.

Section 15: Copyright Notice

Kaiju Codex. © copyright 2015 Rite Publishing Steven D. Russell; Authors Elaine Betts and Justin P. Sluder

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