Lethal Hunter

Free action

Once per battle as a free action, choose an enemy. The crit range of your attacks against that enemy expands by 2 for the rest of the battle. A mob of mooks counts as a single enemy.

Adventurer Feat: 

The crit range of your Lethal Hunter attacks expands by 1 (to +3).

Champion Feat: 

One battle per day, you can use Lethal Hunter against two different enemies.

Epic Feat: 

Your Lethal Hunter crits deal triple damage instead of double damage while the escalation die is 3+.