Metathran Birthing Chamber

Indestructible
Whenever a creature with a static ability enters the battlefield put a counter on Metathran Birthing chamber
At the beginning of your precombat main phase add {x} mana to your mana pool where {x} is the number of counters on Metathran Birthing chamber.
If Metathran Birthing Chamber has 5 or more counters on it exile it and return it to the battlefield transformed under its owner's control.