What did Guph promise the Chief Whimsie in return for his help?

Guph promised the Chief Whimsie that he would grant him the power to rule the land of the Whimsies and to have control over the other whimsical creatures. This appeal to ambition and desire for authority motivated the Chief Whimsie to assist Guph in his plans. The promise of power was a key factor in securing the Chief Whimsie's loyalty and cooperation.