The Gravemind

Whenever a creature you control becomes blocked or gets blocked, put a flood token on target creature opponents controls.
{t}Target opponents exiles X cards from the top of their library, where X is flood tokens target opponent controls.
If a creature is revealed, you may play that card without paying it's mana cost and it becomes a 4/4 flood in addition to its other types.
target opponent puts each other card exiled this way
on the bottom of their library.