Sleeper, Exploring Symbiote

Host{2}{u}{b}(If you cast this spell for its host cost, put it over target creature you control. This creature gain all abilities from the creature under it.)
———{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}
Wither
Regenerate Sleeper {u/b}{u/b}{u/b}

Whenever a creature with a -1/-1 counter on it dies,
Sleeper explores, then sleeper deals damage equal to its power to target that creature's controller