Malthis, Soulcatcher

Delve. Creature cards exiled this way are exiled
with a corpse counter on them, and Malthis,
Soulcatcher enters the battlefield with a -1/+1
for each card exiled this way.
{b}, {t}: Remove a -1/+1 from Malthis,
Soulcatcher. Then, if Malthis, Soulcatcher has
no -1/+1 counters on it, you may cast any
number of creature cards with corpse counters
on them from exile without paying their mana
costs until end of turn.