Savviro, Dimir Executor

Partner with Amabard, House Physician
Whenever Savviro attacks or blocks, you may
sacrifice a creature. If you do, Savviro gains
double strike and menace until end of turn.
Whenever a creature an opponent controls dies,
if it had any -1/-1 counters on it, create that
many 1/1 black Skeleton creature tokens.