Soulbound Spirit

Linger (When this creature dies, you may exile it. If
you do, create a token that's a copy of it, except it's
1/1, it's a Spirit in addition to its other types, and it
has flying.)
Soulbound Spirit can't be blocked except by
Spirits.
Whenever another Spirit enters the battlefield
under your control, Soulbound Spirit gets +1/+1
until end of turn.