Onyx Dog

A figurine of wondrous power is a statuette of a beast small enough to fit in a pocket. If you use an action to speak the command word and throw the figurine to a point on the ground within 60 feet of you, the figurine becomes a living creature. If the space where the creature would appear is occupied by other creatures or objects, or if there isn’t enough space for the creature, the figurine doesn’t become a creature.

This onyx statuette of a dog can become a mastiff for up to 6 hours. The mastiff has an Intelligence of 8 and can speak 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.