Take note that the ones on Fjordur are technically cave creatures and aren't meant to be tamed. Because of this their stats tend to bug out often and they get a inventory bug where you can't move the items in their bigger form until they revert back to their small form. (So make sure to turn off harvesting) You can however find them spawn up to 300, which when tamed will go to 450, meaning you can get some very powerful ones without having to breed any generations, if you're feeling rather lazy.

More Ferox Taming & KO Tips