His rule of Lanlak came to an end when he was sought by the world-devouring Galactus to serve as his newest Herald. Galactus sent his sometimes-adversaries of the Fantastic Four to apprehend Tyros and bring him to receive the Power Cosmic. Tyros resisted them, but to no avail. Galactus made Tyros his new Herald Terrax, and the power cosmic magnified his abilities,making him far more powerful than he had been before. Terrax proved to be the most troublesome Herald to ever serve Galactus. Although he led to devour many worlds, Terrax wished to use his powers for personal gain, and only fear of his master kept him in line. He once fled Galactus' service to set up his own empire, but Galactus empowered the Earth woman, Alison Blaire (also known as Dazzler) to retrieve him. Finally, Terrax kept Galactus from feeding long enough that his energies dwindled, and he finally led him to Earth in the hopes that the Fantastic Four would help him slay his master. Galactus withdrew the power Cosmic from Terrax to replenish his own spent energies, and left Terrax stranded on Earth.

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