If you pursue both Triss and Yennefer in a single run through Witcher III–you told Triss you loved her after Now or Never, and told Yennefer you loved her after The Last Wish–you’ll open a new quest called It Takes Three to Tango that triggers after you complete Final Preparations.
It’s worth seeing the results here at least once, but it permanently ends your relationships with both Triss and Yennefer, as well as your chance to see either of their endings. You’ll end up with the vague bummer of a finale where Geralt continues his lonely life as a wandering Witcher.
The rest of the romanceable women in Witcher III are one-time affairs and side quests. You can pursue any or all of these liasons, and spend as much time as you like in the brothels of Novigrad and Beauclair Port, without affecting your relationship with Triss or Yennefer.
After you complete Hunting a Witch and Wandering in the Dark, you’ll receive an invitation to visit Keira Metz at her home, a hut northeast of Midcopse. There, she offers you the quest A Towerful of Mice.
Complete it, and its followup Favor for a Friend, and Keira will invite Geralt over for dinner. You can opt to become “friends with benefits” with Keira after the meal.
Go to the fighting ring east of Harviken and pick up the Iron Maiden side quest, which requires you to fight Jutta an Dimun. If you’ve defeated Olaf already, during the Fists of Fury secondary quest in Skellige, Jutta will agree to fight you directly.
Otherwise, she’ll make you undertake a random task in order to prove you’re not just some nobody, such as defeating Einar or Gundar in Harviken in a fistfight.
When you earn the right to take Jutta on, don’t use any of your Witcher tricks during the fight, like bombs, potions, or signs, or you’ll fail the quest on the spot for being unsporting. (You can stack the deck by drinking potions to buff yourself before the fight, however; Jutta only cares if you drink a potion while you’re fighting her.) You also only get one shot at completing Iron Maiden; if Jutta beats you, Iron Maiden will fail and she won’t offer you a rematch.
Jutta will give in once you reduce her to 25% health or lower. It doesn’t matter what you say when she asks you where you learned to fight; however you answer the question, she’ll ask you to meet her at her place after dusk. Stop by there after 8 PM, and she’ll proposition you.
Read the notice board near St. Gregory’s Bridge in Novigrad to begin the High Stakes side quest. To continue it, head to the Passiflora and pay 1,000 crowns to enter the gwent tournament there.
The more information outcome of the tournament doesn’t matter for the purposes of this quest. Once it concludes, regardless of who won, the scribe announces that the prize money has been stolen. Sasha, one of the other players, will offer to team up with Geralt to find the thief. Agree to help her out.
At the end of the quest, Sasha will invite Geralt to dinner. If you turn her down, the quest ends on the spot. If you dine with her, you have the additional option to romance her, although she won’t be there the next morning.
The love scene with Syanna is exclusive to the Blood and Wine expansion for Witcher III, which is included in the Complete Edition.