I have done some research about Mati and have reported my findings here.
Mati is greek for "Evil Eyes". Mati was named by Noah. Mati has no spawner and cant be caught. Mati will disappear when aproached.his distinguishable feature is his haunting glowing red eyes.they tend to appear at eye level with the player.they have no noticable pupils in its dark gaze.
Mati was at first thought to be stars in odd paterns, but it soon became evident that that it was something much differenit. He has been described in many ways . In one description he is a large pair of eyes with round pupils. In another report he is said to be a ghostly form. But perhaps the most reported description (and the one with pictures)is i with large unpupiled eyes.
I noted that the place with the most sightings is the ocean. In one account the player was swimming around looking for kelp for his elevator, when Mati apeared in front of him,and ,in a flash,Mati was gone