Spellcasting takes a toll, and can only be normally performed a certain amount of times per day before the strain is too great. You can push through the strain and endure it thanks to Adrenaline in order to cast a few more spells per day.

• Increase your Constitution score by 1, to a maximum of 20.
• You can cast any spell you have known or prepared using Adrenaline Points. This casting of that spell doesn't cost a spell slot, but instead you must spend Adrenaline Points equal to twice spell's level. The highest level of spell you can cast using this feature is equal to half your proficiency bonus, rounded down. This casting of that spell still costs all of the components it normally costs. You can cast spells using this feature twice per long rest.