The Stygian Aerie is a dungeon in Act II of Torchlight II, located in the Ossean Wastes. It may contain Champion Dune Mothers and Champion Basilisks.
The Manticore and the Manticore's Mate reside on the second level. Killing the Manticore will give you the achievement "Manticore", killing the Mate unlocks "Who's Your Friend".
Part of the Sphinx's challenge in order to access the Forsaken Vaults. This can be done before receiving the quest.