Morolaath

The Blind Wolf is a Halo creature that didn't make it into Halo: Combat Evolved. It can be seen in the Halo 2 Collector's Edition Disc. You were able to mount it and ride it. A reason they didn't put it in gameplay is because you couldn't control it. This is speculated by Bungie saying they couldn't handle it on the AI side. That is also another reason they didn't add it to the game.