Head to the small arena near the north center of the zone. Gladion, a 27 epic x2 minotaur, is in the middle of the arena, and three 27^^ Reverent Controllers are on the surrounding ledges. Gladion is not aggro by himself, nor is he linked with the Controllers, but attacking either Gladion or the Controllers causes both to attack you.
The cage is under a ledge at
( 135, -48, 749 ) Copy/waypoint 135, -48, 749. Once you grab it, a roekillik sandbagger will appear, stun you and snatch the cage away.
Upon entering, take the left path. It is guarded by the same groups of roekillik in the previous quest.
Once you reach the mine elevator room, take the north tunnel. Half way in is a group of two roekillik miners^ and a foreman^^. At the end of the tunnel is a room, guarded by an epicx2 greater rumbler. Behind and to the left of it is a small, antique cage. Grabbing it will summon a roekillik sandbagger, who snatches it away from you.