This power can be used to cure the huntress and spirit, however, if the timer on it is not up yet, and you try to preserve either the huntress or spirit, it says you've already done that, but still takes away (gasp) 120 mana.

The effort of making the attempt is enough to drain you of the required mana. There's plenty of skills/supps/powers out there that do the same thing.

Kastellyn the Devourer of Magic, Lord of Legends