Nahiri, Forged in Fury - 36 M MAT

Affinity for Equipment (This spell costs {1} less to cast for each Equipment you control.)
Whenever an equipped creature you control attacks, exile the top card of your library. You may play that card this turn. You may cast Equipment spells this way without paying their mana costs.

mythic
Legendary Creature — Kor Artificer
From the Magic: The Gathering set March of the Machine: The Aftermath.