The Bleeding Phoenix

Flying
When The Bleeding Phoenix enters the battlefield, create X 2/2 Bloodspawn Tokens with
"if a creature was dealt damage by a Bloodspawn this turn, create a Bloodspawn Token" where X is the number of creatures on the battlefield.

Call of The Phoenix-{w/b}{b/r}{r/g} As an additional cost
to this ability, Sacrifice X Blood Tokens.
—All Bloodspawn have +X/+X until end of turn