Medium fiend, neutral evil

Armor Class 18 (natural armor)
Hit Points 135 (18d8 + 54)
Speed 30 ft.

22 (+6) 12 (+1) 17 (+3) 17 (+3) 13 (+1) 21 (+5)

Saving Throws Dex +7, Wis +7, Cha +11
Skills Arcana +9, Insight +7, Perception +7
Damage Resistances cold, lightning
Damage Immunities necrotic; bludgeoning, piercing, and slashing damage from nonmagical weapons
Condition Immunities charmed, exhaustion, frightened
Senses darkvision 60 ft., passive Perception 17
Languages Abyssal, Common, Celestial, Dwarvish, Infernal
Challenge 17 (18,000 XP)

Special Traits

  • Hidden Soul. A creature holding the egg containing Koschei’s soul can use an action to compel Koschei as if a dominate monster spell were cast on him and Koschei failed his saving throw. As long as the soul is within the needle, Koschei can’t permanently die. If he is killed, his body reforms in his lair in 1d10 days. If the needle is broken, Koschei can be killed like any other creature.
  • Innate Spellcasting. Koschei’s innate spellcasting attribute is Charisma (spell save DC 19, +11 to hit with spell attacks). He can innately cast the following spells, requiring no material components.
  • Legendary Resistance (3/day). If Koschei fails a saving throw, he can choose to succeed instead.
  • Magic Weapons. Koschei’s weapon attacks are magical and do an extra 14 (4d6) necrotic damage (included below).


  • Multiattack. Koschei makes two longsword attacks and one drain life attack.
  • Longsword. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 10 (1d8 + 6) slashing damage or 11 (1d10 + 6) slashing damage if used in two hands plus 14 (4d6) necrotic damage.
  • Drain Life. Melee Spell Attack: +11 to hit, reach 5 ft., one target. Hit: 20 (4d6 + 6) necrotic damage. The target must succeed on a DC 19 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken from this attack, and Koschei regains an equal number of hit points.

Legendary Actions

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

  • Attack. Koschei makes one attack with his longsword.
  • Teleport. Koschei teleports to an unoccupied space he can see within 40 feet.
  • Drain (2 actions). Koschei makes one attack with Drain Life.


Koschei’s lair is the crumbling remains of his ancient castle.

Though there are still finery and riches contained within the structure, Koschei seems oblivious to the march of time threatening to demolish his home.

Lair Actions

On initiative count 20 (losing initiative ties), Koschei takes a lair action to cause one of the following effects; Koschei can’t use the same effect two rounds in a row:

  • Koschei creates a whirlwind centered on a point he can see within 100 feet. The whirlwind is 10 feet wide and up to 50 feet tall. A creature in the area of the whirlwind when it’s created, or who enters the area for the first time on a turn, must make a DC 15 Strength saving throw. On a failed save, the creature is restrained and takes 18 (4d8) bludgeoning damage from the buffeting wind. A restrained creature can escape from the whirlwind by using its action to repeat the saving throw; on a success, it moves 5 feet outside the area of the whirlwind. The whirlwind lasts until Koschei uses this action again or dies.
  • Tortured spirits appear and attack up to three creatures Koschei can see within the lair. One attack is made against each targeted creature; each attack has +8 to hit and does 10 (3d6) necrotic damage.
  • Koschei disrupts the flow of magic in his lair. Until initiative count 20 on the following round, any creature other than a fiend who targets Koschei with a spell must make a DC 15 Wisdom saving throw. On a failure, the creature still casts the spell, but it must target a creature other than Koschei.

Regional Effects

The region containing Koschei’s lair is warped by Koschei’s magic, which creates one or more of the following effects:

  • Rabbits, ducks, and other game animals become hostile toward intruders within 5 miles of the lair. They behave aggressively, but only attack if cornered. Foraging for food by hunting is difficult and only yields half the normal amount of food.
  • Wind and snowstorms are common within 5 miles of the lair.
  • Koschei is aware of any spell cast within 5 miles of his lair. He knows the source of the magic (innate, the caster’s class, or a magic item) and knows the direction to the caster.

If Koschei dies, conditions in the area surrounding his lair return to normal over the course of 1d10 days.


This wizened old man is little more than wrinkled skin stretched taut over bones. His long, wispy white hair is surmounted by a crown, and he wears a gold-trimmed black robe. A large sword with a twisted blade rests in his nearly skeletal hand.


Koschei, the king of an ancient land, feared death so much that he turned to the darkest magic to stave off his demise. He discovered a means to protect himself from both time and injury, and transformed himself into something both greater and less than human. Similar to the transformation into a lich, Koschei became an immortal fiend. He remains terrified of death, and his appearance has become withered and ancient despite his vigor.

Undying Secret. Koschei cheated death by separating his soul from his body and hiding it in an iron chest, buried beneath a tree on an island. In the chest is a rabbit, which immediately tries to flee if the chest is opened. If the rabbit is killed, a duck flies out from the chest and tries to escape (use hawk statistics, can’t attack). If the duck dies it lays a green egg, inside of which is a golden needle that contains Koschei’s soul. As long as his soul is safely hidden away, time and death slide past the undying king.

Section 15: Copyright Notice

Tome of Beasts. Copyright 2016, Open Design; Authors Chris Harris, Dan Dillon, Rodrigo Garcia Carmona, and Wolfgang Baur.

This is not the complete section 15 entry - see the full license for this page