Driller

You are frighteningly quick and accurate in combat, granting you the following bonuses:

• Increase your Strength or Dexterity by 1, to a maximum of 20.
• Once per turn, when you hit a creature with an attack that deals piercing damage, you can reroll one of the attack’s damage dice, and you must use the new roll. This stacks with the re-roll given by the piercer feat. You may use this on the same attack as one you use the re-roll from piercer with. 
• When you score a critical hit using a piercing weapon, you may make an additional attack against the same target, or a target 5 feet or less behind it, if the critical hit killed the first creature. If you attack the secondary creature, you move enough distance that you can attack it, but no more. This doesn’t require movement, although it does provoke opportunity attacks as normal.