The Grower was a figure that the Watcher prophesied would help give D'ni new life. According to the Watcher, the Grower would have the abilities to link at will, bring new light to the cavern, and link through time, among other things.
Several of the D'ni have tried to claim that they were the Grower. Kadish built the age of Ahnonay to convince people he could travel through time, as well as Er'cana to produce pellets that would bring light to the cavern. Esher was also convinced he was the Grower, using a skin patch of a Bahro to link at will.
In 2004, it was revealed that in fact, Yeesha was the actual grower. She has mastered to link at will in various places, to link through time by writing a book to an alternate version of the Kadish Tolesa vault, and to bring light to the cavern in the end of Uru: The Path of the Shell.