Mirdane was an ancient Quintesson who was banished into another dimension by his comrades for being a criminal. The exact nature of his crime—and his body type—is unknown.
After the Autobots discovered the secret chamber in Planetary Corridor CB311B4, Rewind examined the hieroglyphics and learnt that the room was used by the Quintessons to banish their criminals to other dimensions. The writings on the wall said that Mirdane was banished to a dimension without substance.
- Mirdane is never seen, only mentioned. Poor guy.