Gray Wolf

Gray Wolf is Tiger's brother in the Monster Rancher anime. He looks just like him except he's completely grey. Gray Wolf was once like his brother Tiger and has pretty much the same attacks. One day, Moo took Gray Wolf away from Tiger. Tiger later found out from a worm that Moo made Gray Wolf into one of his Big Bad Four.

After his many minions were defeated by Genki's group, Gray Wolf challenged Tiger to a one on one duel. While Genki and the other Searchers fought against Gray Wolf's pack of Cabalos (a cross between a Tiger and a Naga) Tiger fought Gray Wolf. They both used their Tornado attacks, then their Ice Beams. They fought all the way up to a hill where they agreed to use their claws against each other to break the tie. But as they jumped at each other, Gray Wolf instead whipped Tiger in his eyes, blinding him. Tiger said he taught his brother that move. Gray Wolf gave one chance for Tiger to turn evil. He declined, so Gray Wolf hit him with his Ice Beam twice. Genki ran over to Tiger and Gray Wolf ran at them. Tiger could sense Gray Wolf's vibrations, so he ran at him and stabbed him in the throat with his horn, shattering his Moo medallion.

The two brothers reonciled after the Cabalos ran away, Tiger saying his plan was always to win Gray Wolf back from Moo. In some flashbacks, it is revealed that Tiger helped Gray Wolf get his food back from some bullies, and the time when he took some meat from Gray Wolf he gave it back to him saying he wasn't really hungry. After these flashbacks, Gray Wolf turns to a Lost Disc. But he returned in the future like the other dead monsters once Moo was destroyed.