The Ultra Breeding Tree functions as a functional duplicate of the Breeding Mountain, and can be used with the Breeding Mountain giving you the ability to breed two sets of monsters at the same time. This allows you to do things like breeding monsters for upgrading your Gold production, while at the same time breeding for a rare monster that is still breeding (with only the Breeding Mountain you can't do this). Another thing that you can do with this is breeding two sets that have a chance of making the monster that you desire, increasing or doubling your chances of breeding the desired monster. As it is beneficial to players, the Ultra Breeding Tree costs 150 Gems, unlike the Breeding Mountain which costs 150 Gold.