Strength Among Legion

Changeling (This card is every creature type.)
Materialize {w}{u} (You may pay an additional {w}{u} as you cast this spell. If you do, put it onto the battlefield as it resolves as a creature. It loses all other
card types.)
Creatures you control gain solidarity until end of
turn. (Those creatures get +1/+1 for each other
creature you control that shares a creature type with
them.)