Demonica, Succumbus

Whenever Demonica enters the battlefield, each
player may sacrifice another creature to search
the library for a card and put it into their hand.
Shuffle libraries afterwards.
Whenever Demonica would kill a creature in
combat, gain control of that creature instead of
putting it in the graveyard. If Demonica leaves
the battlefield, put all creatures you gained
control of with this ability into their
owners graveyard.