Baleful Recharge is an extremely useful passive ability for all mages. It converts 3% of the damage you deal to enemies into mana. Thus character recovers mana pool much faster.
3% is not a small value at all. You will get 3 mana points from each 100 damage dealt. This passive makes AoE abilities even better, allowing you to benefit not only from massive damage but also from mana recovery.
This ability is a must have for any character with any role. Extra mana regeneration is always great and will help in battle. The greatest advantage is that this bonu is prmanent and doesn't require activation.