Maddening Hex
Source: Xanathar’s Guide to Everything
Prerequisite: 5th level, Hex or a Warlock feature that curses
As a bonus action, you cause a psychic disturbance around the target cursed by your hex spell or by a warlock feature of yours, such as Hexblade’s Curse and Sign of Ill Omen. When you do so, you deal psychic damage to the cursed target and each creature of your choice within 5 feet of it. The psychic damage equals your Charisma modifier (minimum of 1 damage). To use this invocation, you must be able to see the cursed target, and it must be within 30 feet of you.