I was playing the following deck
6 devourers
4 fractals
6 aether pillars
6 drain lifes
8 obsidian pillars
mark of aether
Waited until my last turn, and my opponent got me down to 1 HP. Played my drain lifes. Elemental Mastery.
Of course, this deck can't help but get elemental masteries every time it wins (which is surprisingly often, and much more so with a few shards), unless your opponent plays eclipse.