He is an adult male Yoshi who came to live with Morton Jr., along with his little brother, Pebble Yoshi, whom Morton Jr named after he adopted them as a reward for saving Yoshi Isle from the Bomb explosion threat.

Eventually, when Basalt starts talking, He has a soft-spoken, deep, and gravelly voice that contrasts with his menacing, beast-like appearance. He rarely speaks, communicating in short, clipped sentences, grunts, and growls that highlight his reserved, stoic, and protective nature.