Muoni, Siphon of Souls

Whenever a non-Spirit creature you control dies, return it to the battlefield under your control. That creature gets -1/-1 and is a Spirit in addition to its other types.
{b}{b}: Put a -1/-1 counter on target creature and
a +1/+1 counter on Muoni, Siphon of Souls.
{w}, Exile target Spirit you control: Regenerate Muoni.