Kathound, Master of Spirits

Flying, indestructible
When you cast Kathound, Spirit of Evil, take
control of all spirits for as long as it remains on
the battlefield.
At the beginning of your upkeep, you may reveal
Kathound, Spirit of Evil from your hand. If you
do, target creature you don't control becomes a
Spirit in addition to its other types. Then, put a
+1/+1 counter on that creature.