Allies?

As this enchantment enters, choose a creature type. Creatures you control are the chosen type. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.

Changeling (This card is every creature type.) Creatures target player controls get +0/+1 and gain all creature types until end of turn.

Whenever this creature or another Ally you control enters, you may have target player lose life equal to the number of Allies you control.

: Put target creature card from an opponent's graveyard onto the battlefield under your control if its mana value is less than or equal to the number of Allies you control.

Whenever this creature or another Ally you control enters, target player mills X cards, where X is the number of Allies you control.

: Add X mana of any one color, where X is the number of Allies you control.

You may have this creature enter as a copy of any Ally creature on the battlefield.