The Forlorn Sabertooth pet has a very cool design! (It's a Death reskin of Sabertooth). But unlike Frost fang (also a reskin of the Sabertooth, for Ice), it does not have its own spell and mount.
I think you could make an item card spell for the Forlorn Sabertooth pet which does death damage, since you did the same for the Frost fang pet, and mount.
And I think if there was a mount made of Forlorn Sabertooth it would be very successful and many players would want it.