Havengul Lich

The cleverest part of this engine isn't that it reanimates: plenty of cards drag creatures out of graveyards. It's the second clause, the one that hands the Lich every activated ability of whatever it just cast. Cast a creature with a sacrifice outlet and the Lich becomes the outlet; cast one with a tap ability and the Lich gets it too, all until end of turn. The repeatable cost means the graveyard becomes a stack of one-shot spells you can fire each turn, and because you're casting the card rather than putting it onto the battlefield, the creatures enter as castable spells subject to all the normal ways casting matters. The body matters less than the toolbox it operates: any graveyard works, yours or an opponent's, so the Lich quietly turns a board wipe into a buffet. The design tension is that everything it does is mana-gated and incremental, never explosive, which is why it reads as a grind engine rather than a combo piece on first inspection (though pairing it with the right creature loop and a sacrifice payoff has always been where the danger lives). It sits in a small family of casts-from-graveyard engines that reward a deck built around cheap, individually-useful creatures with abilities worth borrowing, and it's the rare member of that family whose ability-stealing rider makes the Lich better each time it reanimates a creature.