Niffis Fighting Pits (Portal Gem)
From Drunkapedia
The portal gem drops randomly on Banderling Predators, Banderling Scalpers and Banderling Aggressors. A gem can also be purchased from the Colosseum Coin Collector.
Opens a portal to the Niffis Fighting Pits (dungeon), a part of the Niffis Fighting Pits quest.