A lot of the time when i am in battle i tell my friends to port and they help me. and alot of the time they dont have any mana so i am thinking maybe you guys could make a side quest from zeke in krokotopia where we would do a quest to get a spell that when you pay 300 health to give 50 mana to your buddy.
As much as i like this idea, it cannot happen. Due to the fact you can get mana by catching wisps, buying potions, and lastly playing mini games. You can get mana three ways without sacrificing health, be prepared for battles and you wont even need a spell like that.