Phyrexian Obliterator

Trample
Whenever a source deals damage to Phyrexian Obliterator, that source's controller sacrifices that many permanents of their choice.

Grim Return

Choose target creature card in a graveyard that was put there from the battlefield this turn. Put that card onto the battlefield under your control.

Pulse of the Dross

Target player reveals three cards from their hand and you choose one of them. That player discards that card. Then if that player has more cards in hand than you, return Pulse of the Dross to its owner's hand.

Mindslaver

{4}, {T}, Sacrifice Mindslaver: You control target player during that player's next turn. (You see all cards that player could see and make all decisions for the player.)

Cruel Entertainment

Choose target player and another target player. The first player controls the second player during the second player's next turn, and the second player controls the first player during the first player's next turn.

Fraying Omnipotence

Each player loses half their life, then discards half the cards in their hand, then sacrifices half the creatures they control of their choice. Round up each time.

Herald of Leshrac

Flying
Cumulative upkeep—Gain control of a land you don't control. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Herald of Leshrac gets +1/+1 for each land you control but don't own.
When Herald of Leshrac leaves the battlefield, each player gains control of each land they own that you control.