You gain the ability to use a bonus action to lower your Constitution Ability Score lower to 8 and you add half of those ability score to your spell casting Ability Score for 1d10 turns per combat. Usable twice per long rest. 

Example: You are a Sorcerer have 16 Constitution and 16 Charismas. When using this ability, the CON stats lower to 8 and your CHA increase to 20.