The latest Dragonflight alpha build added a proto-drake mount model resembling Raszageth, the final boss of the Vault of the Incarnates raid. Could this be a mount from the raid?
This new dragon model comes with a saddle addition and mount-specific animations like /mountspecial which you can preview below in our model viewer.
Raszageth is the main antagonist of the early Dragonflight story, a proto-dragon of immense elemental power freed by the Primalists in the Dracthyr starting experience.