The best place to farm Lifeforce Orbs
is in the Everlight Facility
, after you open the main gate and enter with the Overlord
you will see a prison full of gnomes
to your left, just open and hold
towards the opening that your minions will kill them and capture Lifeforce Orbs, it is highly recommended that you use The Evil Eye
helmet, which doubles the amount of Lifeforce Orb obtained.