Mana Feed

Mana Feed was a Warlock talent in the Demonology tree that caused the warlock to gain mana when the Warlock's demon critically hit, and caused Life Tap to also restore a percentage of the gained mana to the Warlock's pet.

Mana Feed was especially useful for grinding, where the paltry mana totals of a Voidwalker or Felguard might come up a bit short, or to recharge the waning mana of the Felguard or Imp during long battles.

Combined with effects like Siphon Life (Classic), this could turn your pet into an almost inexhaustible mana battery.