Based on the excerpts from "Metamorphoses" by Ovid and "The Tempest" by William Shakespeare, the power that both Prospero and Medea have is they can control wind.
In the excerpt from Ovid's "Metamorphoses," Medea calls upon various elements of nature, including breezes and winds, signifying her ability to control them. Similarly, in "The Tempest," Prospero wields power over storms and the natural elements, indicating his command over wind as well. Thus, both characters share the ability to manipulate wind and the forces of nature.