Wall of Frozen Souls

Defender, Indestructible, Cascade, cascade,
cascade, cascade
(When you cast this spell, exile cards from the top of
your library until you exile a nonland card whose
mana value is less than this spell's mana value. You
may cast that card without paying its mana cost if the resulting spell's mana value is less than this spell's
mana value. Then put all cards exiled this way that
weren't cast on the bottom of your library in a random
order. Multiple instances of cascade trigger separately