Borgir, the Catalyst

Borgir has Ward {x}, where X is the number of legendary artifacts you control.
Whenever you cast a legendary artifact spell, you
may pay {u}{b}. If you do, reveal cards from the
top of your library until you reveal a legendary
artifact spell. Exile it and put the rest of the cards
on the bottom of your library in any order.
You may cast legendary artifact spells exiled with Borgir as if they had flash.