Dwebble, Shy Scuttler

Whenever a Crab enters the battlefield under
your control, create a colorless Equipment artifact
token named Shell with "Equipped creature has
+0/+1 and shroud" and equip {1}.
At the beginning of your end step, if you control
4 or more Crabs, transform Dwebble.
{t}: Dwebble gains indestructible until end of
turn.