This is part of my “Pyre” world.
The orbs wander the ruins of Pyre randomly. When they near anyone that they deem a danger, they unleash bolts of lightning that spread throughout the ground up to 6 yards away. Any living creature standing on the lightning-infused ground takes some damage and is held immobile where they stand. An exceptionally strong individual may be able to muster enough strength to manage a ranged attack while held immobile.
Worse, while the lightning dissipates within seconds, all immobilized creatures remain immobilized until the Orb is destroyed or chooses to move on.