unidentified plans egg

{1}{w}: create a 0/1 bird token with defender
when a creature enters the battlefield permanent strength counter on Unidentified plans egg.
When Unidentified plans egg has 5 permanent strength counter on it. exile Unidentified plans
egg remove half the permanent strength counter rounded up, and return to to the battlefield transformed.
Hatchery(can be a commander with any number
of creatures with hatchery)