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Gift to Avernus
warlock attack 1

Target: one creature

Attack: Charisma vs. Reflex

Hit: "1d10 + Charisma modifier damage."
Level 21: "2d10 + Charisma modifier."

Miss: "You can choose to take damage equal to your level to reroll the attack roll. You can choose this only once each time you use this attack."[Dr386:46]

Gift to Avernus is an at-will power available to warlocks at 1st level. Either gift to Avernus or hellish rebuke is granted automatically to warlocks who choose the infernal pact option for their Eldritch Pact.

Gift to Avernus was introduced in "Class Acts: Dealers in Deviltry: Crimson Knights of Bael Turath" by Mike Mearls in Dragon #386.

It is considered a good choice, as the miss effect allows you to become highly accurate, at the cost of taking damage (which both overlaps with the infernal pact boon, and may be worded to allow resistance). [1]