When this Dinosaur enters the battlefield or attacks, you get to spit up a -1/-1 counter on a creature
Marauder aside, this is probably the new best creature in Golgari Self-Mill overall
However, effects that stop a creature from untapping "during your untap step" or "during its controller's untap step" won't stop that creature from untapping during another player's untap step, and as such, Prop Room's ability will cause that creature to untap
Did Teenage Mutant Ninja Turtles kill the game for you
What keeps this from being truly bonkers is that often players wont attack anyway and are content to leave guys back on defense and play for the long game
Tasha doesnt really have a game-winning ultimate, but I do think its still worth running The Chain Veil to keep activating the +1 ability to draw a card and stock Tashas spellbook