As a reaction, when a creature you can see falls unconscious (form dropping to zero hit points) or dies, you can drain some of their lifeforce as it leaves their body. You gain access to one of their abilities (either innate or granted by a class) and can magically reproduce it. You may choose to take an ability that you have witnessed them perform, or you can choose to have the DM randomly assign you an ability that you are unaware of.   You keep the ability until you choose to activate it (following the same rules as found in the original creature's stat block) or break concentration. Activating the ability is a free action. If the ability forces a save of any kind, you must use the save of the creature that you stole the ability from. Once used, you can use the stolen ability for one minute.