During your turn, when you attack a staggered enemy you were not engaged with at the start of your turn, deal +1d6 damage per level to that creature if you hit.

Adventurer Feat: 

You gain a +2 bonus to Slayer attacks.

Champion Feat: 

Once per battle, when you miss with a Slayer attack, deal the additional +1d6-per-level damage to the target instead of normal miss damage.

Epic Feat: 

Whenever one of your Slayer attacks drops a non-mook enemy to 0 hp, you gain 20 temporary hit points.