Innate Spellcasting: The boneclaw's innate spellcasting ability is INT (+7 to hit, spell save DC 16)
3/day: vampiric touch
1/day: enervation
At will: chill touch (3d8)
Rejuvenation. While its master lives, a destroyed boneclaw gains a new body in 1d10 hours, with all its hit points. The new body appears within 1 mile of the boneclaw’s master.
Shadow Stealth. While in dim light or darkness, the boneclaw can take the Hide action as a bonus action.
Unholy Fortitude. Whenever the boneclaw regenerates health as part of a spell or ability that deals necrotic damage, double the amount of health regenerated. The boneclaw does not gain this bonus if it took radiant damage since the end of its last turn.
Multiattack. The boneclaw makes two attacks with either its claws or its sludge blood. It can only make one attack if it is currently grappling a creature.
Piercing Claw. Melee Weapon Attack: +8 to hit, reach 15 ft., one target. Hit: 20 (3d10 + 4) piercing damage. If the target is a creature, the boneclaw can pull the target up to 10 feet toward itself, and the target is grappled (escape DC 14). The boneclaw has two claws. While a claw grapples a target, the claw can attack only that target.
Sludge Blood. Ranged Weapon Attack: +7 to hit, range 30/120 ft., one target. Hit: 16 (2d12 + 3) necrotic damage.
Shadow Jump. If the boneclaw is in dim light or darkness, each creature of the boneclaw’s choice within 5 feet of it must succeed on a DC 16 Constitution saving throw or take 34 (5d12 + 2) necrotic damage.
The boneclaw then magically teleports up to 60 feet to an unoccupied space it can see. It can bring one creature it’s grappling, teleporting that creature to an unoccupied space it can see within 5 feet of its destination. The destination spaces of this teleportation must be in dim light or darkness.
Dark Regeneration (Bonus Action). The boneclaw instantly kills one of the lesser undead that it has summoned within 30 ft. of it. It then regains hit points equal to the slain creature's hit point maximum.
Deadly Reach. In response to a visible enemy moving into its reach, the boneclaw makes one claw attack against that enemy. If the attack hits, the boneclaw can make a second claw attack against the target.
You Are In My Domain! (Phase 1). The boneclaw emits darkness from its own evil form. Within 300 feet of the Boneclaw, all bright light becomes dim light and all dim light becomes darkness. This effect persists for 1 hour or until the Boneclaw dies.
Rise From Your Grave! (Phase 2). The boneclaw deals 5 (1d6 + 2) piercing damage to itself and summons an equal number of skeletons from the Shadowfell. The boneclaw is not resistant to this damage. These creatures appear in unoccupied spaces within 30 ft of the Boneclaw and act on the boneclaw's initiative.
Welcome to Your Doom! (Phase 3). The furious Boneclaw sprays its rotten blood in a 20 ft. cone in front of it. All creatures must make a DC 16 DEX save or take 5d12 necrotic damage and become poisoned.