The Thing

Ward —Sacrifice a goaded creature.

At the beginning of your upkeep, put an assimilation counter on target creature. Creatures with assimilation counters are goaded until the end of the game.

Goaded creatures are alien shapeshifters in addition to their other types, and at the beginning of your end step, for each goaded creature an opponent controls, it's controller chooses another creature they control, these creatures must fight.