Mana Stolen Per Hit
From Diablo Wiki
Mana Stolen Per Hit allows you to 'steal' mana from an enemy as long as you can hit them. This is ideal for replenishing mana without the wait and with the fun of destroying your enemies in the meantime. The amount of mana stolen depends on the percentage stolen and how much mana you initially have, if both are high than your mana stolen is also high. Although the initial amount of mana could be higher than one other's with the same amount of mana stolen and get slightly more, the percentage stolen is still fair based upon the initial mana. It is ideal though to have more initial mana so you can recuperate more by attacking.
Mana Stolen is an ideal enchantment for saving mana space for any mana-consuming spells and to lack on the reliability of using potions all the time, saving some profit too. Mana Steal can also help you when your in tough situations with mana burning unique monsters, enabling you to have at least some reserves to use your mana on. Mana Steal is top notch for spell casters and aura users, and is weak if your mana reserves are too low to make a difference on the mana steal or if none of your spells greatly diminishes your mana pool.