This page of The Witcher 3 Wild Hunt answers whether you can romance both Triss and Yennefer at the same time. We explain what will happen when Geralt tries to sleep with both women.
Love triangle with Triss and Yennefer - what can happen?
After returning from Kaer Morhen to Novigrad and completing all preparations for the final battle with the Wild Hunt (Final Preparations), the game will automatically activate the It Takes Three to Tango side quest.
If you have had sex with both Triss and Yennefer before, ladies will now offer Geralt a threesome. You must walk down to the base level of the tavern, buy any high quality wine and go to the tavern called Kingfisher. Yennefer and Triss are waiting in one of the apartments on the first floor.
Ladies must have talked behind Geralt back as they know that he has expressed his feelings to both of them. Sorceress' revenge will be rather humiliating. Our hero will allow himself to be handcuffed to the bed and after an encouraging beginning to some love games, left behind by the ladies...