Dark King Rayleigh

(Durnan of the Yawning Portal)
Whenever Dark King Rayleigh attacks, look at
the top four cards of your library. You may exile
a creature card from among them. Put the rest
on the bottom of your library in any order. For
as long as that card remains exiled, you may cast
it. That spell has undaunted. (It costs {1} less to
cast for each opponent.)