Unnatural Growth

At the beginning of each combat, double the power and toughness of each creature you control until end of turn.

Panharmonicon

If an artifact or creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Vanquisher's Banner

As Vanquisher's Banner enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.
Whenever you cast a creature spell of the chosen type, draw a card.

Realmwalker

Changeling (This card is every creature type.)
As Realmwalker enters, choose a creature type.
You may look at the top card of your library any time.
You may cast creature spells of the chosen type from the top of your library.

The Great Henge

This spell costs {X} less to cast, where X is the greatest power among creatures you control.
{T}: Add {G}{G}. You gain 2 life.
Whenever a nontoken creature you control enters, put a +1/+1 counter on it and draw a card.

Guardian Project

Whenever a nontoken creature you control enters, if it doesn't have the same name as another creature you control or a creature card in your graveyard, draw a card.