Seized Dreams

Each opponent exiles the top X cards of their
library. You may cast cards exiled this way for as
long as they remain exiled, and you may spend
mana as though it were mana of any color to cast
those spells. They cost {x} less to cast.
At the beginning of the next end step, each player shuffles all face up cards they own in exile in
their library.
Exile Seized Dreams.