di'zok escape staff
 

when using the di'zok escape staff it is using the character mana for the clicky on green server draining mana from full at 2318 to 1568 or 850 mana per cast or to zero if not full mana. this is more then the cast cost of the spell.

It casts Evacuate. This spell has a mana drain component that hits for 750 (I think your math was off).

-Mcoy