Drains the enemy of their energy reducing grenade cooldown and adds effects, if you have them, such as replenishing your shield, increasing weapon and speed movement, reducing cooldown for Nova Bomb. Sadly it's whatever effect you choose so make sure you select something that tickles your fancy.

Melee energy drain reduces grenade cd and can heal you if you kill an enemy with it. If you have the skill that makes grenades and supers trigger energy drain they will only reduce grande cd. They won't heal you if you kill an enemy. Good rotation if you have discipline maxed throw grenade, energy drain triggers, wait for it to be gone, then melee, and when energy drain finishes you should have a grenade again. About 12 - 15 second cd then on grenades.

Melee energy drain reduces grenade cd and can heal you if you kill an enemy with it. If you have the skill that makes grenades and supers trigger energy drain they will only reduce grande cd. They won't heal you if you kill an enemy.