Miryath’s First Strike

Heroic Tier
Prerequisite: Wis 13, githzerai
Benefit: The first time you hit a creature that has not yet acted during the encounter, that creature takes extra psychic damage equal to 1 + your Dexterity or Wisdom modifier. The extra damage increases to 2 + your Dexterity or Wisdom modifier at 11th level and 3 + your Dexterity or Wisdom modifier at 21st level.

Published in Player's Handbook 3, page(s) 182.