Elsie Mews, Sharper than the..

Vigilance, Flying, Lifelink, Ward-discard a card
As long as you control an artifact, spells you
cast cost {w}{u}{b} to cast
As long as you control an enchantment, spells you
cast cost {w}{u}{b} less to cast
As long as you control a planeswalker, spells you
cast cost {w}{u}{b} less to cast
As long as you control another creature, spells you
cast cost {w}{u}{b} less to cast