Monster Monday - Boneclaw CR12 Undead that is the result of a wizard's failed attempt to become a lich. https://www.dndbeyond.com/monsters/boneclaw
As a DM, I am in love with this creature for the delicious possibilities it gives me if I have a party member who plays evil a little too evil. I would love to point out one of the creature characteristics from Mordenkainen’s Tome of Foes on this one:
Dark Reflections. A boneclaw’s master might not want such a servant or even know it has one. Boneclaws bind to petty criminals, bullies, and even particularly cruel children. Even if the master is unaware of its new, horrid bodyguard, its local area will be plagued by disappearances and grisly murders, tied together by the common thread of the master’s envy or hunger for revenge.
So if a PC suffers a loss that makes him go dark (I played a Paladin once in a game long ago who succumbed “to the dark side” after his betrothed was brutally murdered by a recurring villain of the campaign), I might well just saddle that PC with one of these lovely monstrosities. In some ways this creature is like the D&D equivalent of The Terminator in that it has a relentless focus on destruction powered by the dark impulses of whatever creature it has chosen for its “master,” even if that master doesn’t know the Boneclaw is there.
Another aspect of this creature I love is its limited immortality. As long as the “master” lives, the Boneclaw cannot be destroyed. If its body is felled, then it reforms within hours and goes back to following the bidding of its master—even if the master doesn’t know that this thing is doing its bidding.
OK fellow DMs, what are some ways you can dream up to use one of these in your campaign?