Opportunity

From wow.incgamers.com

Talent: Opportunity
Effect: Increases the damage dealt when striking from behind with your Backstab, Mutilate, Garrote and Ambush abilities.
Statistics: Rank 1 = +4%, Rank 2 = +8%, Rank 3 = +12%, Rank 4 = +16%, Rank 5 = +20%.