Board Thread:Game Discussion/@comment-154281-20130517134256/@comment-74.101.81.243-20130517134841

You can use any card to upgrade any other card; you could use a MTM Metroplex to upgrade a R3 Optimus, but I wouldn't do it. I don't think you get much more of a benefit using a MTM R2 Razorclaw to upgrade vs a regular R2 Razorclaw, I think you'd be wasting your resources