You can access this area from the Edron Ivory Towers, here. This will cost you a fee, every time you want access. At entrance of the Energy Sphere, there is a teleporter which is the exit back go Edron. There might be up to 3 Charged Energy Elemental near the place you appear when entering, as they spawn near it. The Energy Overlord can be spawned in the south part of the sphere.

The Energy Sphere is the Knight's part of The Elemental Spheres Quest, to get access to it you'll need to use 20 Small Enchanted Amethyst on the Mysterious Machine located in one of the Ivory Towers. You need to have started the The Elemental Spheres Quest, but you can enter this area on your own, no need for players of other vocations.

Energy Sphere

Name	Exp	HP	Max. Damage	Loot
Charged Energy Elemental	450	500	375 (100 , 275 )	0-128× Gold Coin Energy Soil 0-3× Flash Arrow
Overcharged Energy Element	1,300	1,200	875 (200 , 675 )	0-175× Gold Coin Energy Soil Great Health Potion 0-2× Small Amethyst Berserk Potion (rare) Ring of Healing (rare) Wand of Starstorm (very rare)
Energy Overlord	2,800	4,000	1400+	Pure Energy (always) 1-75× Gold Coin 1-3× Platinum Coin 1× Voltage Armor