Share the Spoils

When Share the Spoils enters the battlefield or
an opponent loses the game, exile the top card
of each player's library.
During each player's turn, that player may play
a land or cast a spell from among cards exiled
with Share the Spoils, and they may spend
mana as though it were mana of any color to
cast that spell. When they do, exile the top card
of their library.