Deathmark Dirty Deeds

You have manifested an dragonmark. Determine its appearance. You gain the following benefits:

• Increase your Intelligence score by 1, to a maximum of 20.
• Your dragonmark cause your enemy defense's to become apparent to you for a moment gaining advantage on one attack against that creature.  You may use this ability once per long rest without negative effects, each use after that you take 2 hit dice  of damage that cannot be healed by any means other than a long rest.