The Star Master first appears when Ness has a dream about Poo completing his Mu training. He tells Poo that he is learning a higher power, which is later revealed to be PSI Starstorm. He wishes Poo luck with his training, and disappears.
After Ness and company exit a pyramid in Scaraba, the Star Master appears in a tornado, and tells Poo that the time for him to learn PSI Starstorm is now. Poo leaves the party, and learns PSI Starstorm with the Star Master.
He next appears when Ness first enters Magicant. He is Ness' guide to the world of Ness' mind.
After that, he reappears later and teaches Poo the powerful PSI Starstorm Ω.