A character's mana points are determined by his or her mana stat(s) and Harness Power skill training.
Mana Point Calculation
A character's maximum mana points are equal to the following:
- Max MP = trunc((ManaStat#1+ManaStat#2)/4) + Harness Power Bonus
where the Harness Power Bonus is equal to 3*Ranks for ranks less than or equal to the character's level, and 1*Ranks for ranks beyond the character's level. If the character has only one mana stat, use it for both ManaStat#1 and ManaStat#2.
Versa is a level 10 Elf Empath with a 100 in Influence and a 98 in Wisdom; this amounts to bonuses of +35 in Influence and +24 in Wisdom. Versa has 15 ranks of Harness Power. Versa's maximum mana points are:
trunc((35+24)/4) + 3*(10 ranks) + 1*(5 ranks) = 14 + 30 + 5 = 49 MP.
Official Magic Guide http://www.play.net/gs4/info/magic-guide.asp#mana