This mob spawns at 720, -251 and at the far southwest corner, west of Emerald Jungle zoneline and to the east of Cabilis in that little cutout in the SE.
Just thought I would note that although Festersting will not aggro on his own, he will assist other scorpions that are aggroed. Pulled 4 or 5 trash mobs and Festersting aggroed on me.
This mob is lvl 84 and any scorpion can be a place holder for him. We saw him spawn in many different places around the zone.
Besides the Hooded Eye, he also dropped Unblinking Eye for pure casters- finger slot ac 28 Hp 485 mana 525 slot 7 and a slot 3 with effect Bayle's Purview III