Ra's al Ghul (Batman Arkham Asylum)

First Appearance: Batman Arkham Asylum (Cameo)

Ra's al Ghul is the leader of the League of Assassins and has lived for over 600 years using the powers of the Lazarus Pit.

While Batman is looking for Dr. Young's Titan Formula notes in the Arkham Mansion, he finds his body in a body bag and stored in a morgue. 

The Riddler tagged a riddle to the body to tax Batman and play a game of cat and mouse with his enemy. 

When Batman returns after defeating the Joker, the body has disappeared and the tag is lying on the ground. He most likely was taken to the Lazarus Pit under the Monarch Theater, where he is revived.

Osito (Batman Arkham Asylum)

First Appearance: Batman Arkham Asylum

Ositio was a toy bear that belonged to Bane, when he was a child imprisoned in Pena Duro, Santa Prisca.

He came with Bane to Gotham and eventually found his way to the Arkham Asylum Medical Facility on Arkham Island, where Riddler tied him a riddle that Batman must solve in order to located his position and have him arrested after his escape.