5D Chessboard

Creatures have "{t}: Exile this creature face down.
It gains flash and 'As long as it's the declare
blockers phase during an opponent's turn, you
may cast this spell without paying its mana cost.' Activate only during your turn in the declare attackers phase."
Whenever chaos ensues, exile a card from your
hand or graveyard face down. It gains flash and
"As long as it's the declare blockers phase during
an opponent's turn, you may cast this spell
without paying its mana cost."