From Diablo Wiki
Emikdeva, Siege runekeeper is a Superunique Warscarred Ravager Demon who may spawn (every 3-5 games on average) in Battlefields of Eternity in Act V. The player will find Emikdeva frozen in place along with numerous smaller demons. Smashing the orb will open the eternal prison and activate the demons, beginning The Demonic Prisoner event.
Players must deal with the hordes of trash mobs and kill Emikdeva to complete the event.
- This event will rarely appear as a bounty.
- Emikdeva may drop Skelon's Dice a legendary material used to craft Skelon's Deceit, legendary Pants.
For the first few weeks of Reaper of Souls, this event could be exploited for massive experience gain. The trick was to lure Emikdeva away from the timeless prison, then return to the area. So long as Emikdeva was alive the demons would continue to spawn in great numbers, and they were worth good experience.
Blizzard hotfixed this exploit on April 30th, 2014.
A video showing the exploit can be seen below.