The Lavae Tooth is an item exclusive to Don't Starve Together. The Tooth is dropped from a hatched Lavae Egg. Picking up the Tooth will cause the Lavae that spawned from the same egg to follow you, much like Chester's Eye Bone and Glommer's Flower. Dropping the Tooth on the ground or leaving it in a stationary container will cause the following Lavae to stay by that location. The Lavae will start fires by things he stands near and you can use him to cook, he will also give off a small amount of light, and heat you up if you stand close to him. If the lavae dies the Lavae Tooth will turn to ash.
If Krampus steals this item, the Lavae will start to follow Krampus.