I'm glad mana is only magic energy, and not life force. Though tiring to exhaust mana can only hurt people who are dependant on it by draining it. Any warrior without focus on magic in any way would be safe from such things so the only one that Nia could hurt would be a mage or someone who fights with magic a lot. However I could still see this being a problem for her afflictions to be able to effect friendlies of which (Just saying as a roleplaying "veteran") Could be considered a form of God-Moding simply by the fact that it'd be like character control to simply afflict other peoples characters with a mana drain. If you'd take my advice constrict her mana drain to something like stabbing into a person to suck it out or have it willingly given, and remove her stages from sucking other people passively. Then it'd be a much wider accepted variant. ^.^ Not trying to criticize just saying. I've seen things like this go down many, many times.