body mods - to dual/multiple genitalia

Jaskier knocks on the wrong door one dark and stormy night, the door of a mage obsessed with creating a new broodmare through mutation in order rejuvenate the ancient centaur race. That mage is an idiot, but Yennefer isn’t, and with the aide of the centaurs of Kaer Morhen, Jaskier finds the life destiny plotted for him.