a dimensional anchor  

Found in:

• Executor Vark's Chamber in Obelisk of Ahkzul
• The Executor's Overlook in Anchor of Bazzul

Proximity to this "thing" is reported to extend it's buffs to players and debuffs to the Executors, but this is not confirmed.

Note: we are listing this as a mob with type set to object, rather than as an object, because objects do not generally have buffs on them.