You dont need this knowledge to get the energy!

There's a branch in the abandoned monastery caves where you climb some ledges and past some jail bars you will find a much more difficult group of shadow guards, but there are at least 20 in that branch just be prepared for a higher challenge. The trash loot drops are worth 15,000 if that helps narrow down your in the right spot and to gauge the difficulty. https://imgur.com/a/Cqexna7

Also it should be noted, the knowledge tracking only works on these higher difficulty variety and I was able to get S within 5 minutes with full buffs, pets, and some event knowledge items.

Rare spawn down the well in the Abandoned Monastery. Usually 1-2 up per world. Some world hopping is advised.