Blood Wager

You make a bet with the universe, wagering your life force. Make a ranged spell attack against a target within range. When you hit a creature with this spell, roll a die. On an even result, you take 10d8 necrotic damage, and the target takes double the damage you receive. On an odd result, the target takes 10d8 necrotic damage, and you regain hit points equal to the damage dealt.