Urza's Incubator

As Urza's Incubator enters the battlefield, choose a creature type.
Creature spells of the chosen type cost {2} less to cast.

Akroma, Vision of Ixidor

Flying, first strike, vigilance, trample
At the beginning of each combat, until end of turn, each other creature you control gets +1/+1 if it has flying, +1/+1 if it has first strike, and so on for double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, protection, reach, trample, vigilance, and partner.
Partner

Starnheim Aspirant

Angel spells you cast cost {2} less to cast.

Youthful Valkyrie

Flying
Whenever another Angel enters the battlefield under your control, put a +1/+1 counter on Youthful Valkyrie.

Serra's Emissary

Flying
As Serra's Emissary enters the battlefield, choose a card type.
You and creatures you control have protection from the chosen card type.

Vanquish the Horde

This spell costs {1} less to cast for each creature on the battlefield.
Destroy all creatures.