This onyx statuette of a dog can become a mastiff for up to 7 hours.
The mastiff has an Intelligence of 8 and can understand Common.
It also has darkvision out to a range of 60 feet and can see invisible creatures and objects within that range. Once it has been used, it can't be used again until 7 days have passed.
While being ridden the movement speed of the Onyx dog and the wielder becomes 40 ft.