Friends with Benefits is a miss-able Achievement/Trophy in The Witcher 3 and is unlocked during early game. To unlock the Achievement/Trophy, you need to complete Hunting a Witch and Wandering in the Dark Main Quests.
After defeating the boss in Wandering in the Dark, the woman will ask you to retrieve a lamp which will trigger a Secondary Quest called Magic Lamp, should you choose to accept it! You need to complete ‘Magic Lamp’ before Wandering in the Dark and accept the woman’s invitation!
Simply head inside the woman’s house and complete another Secondary Quest. Following it, you need to complete A Tower Full of Mice and finally another Secondary Quest called A Favour for a Friend.
After collecting all the ingredients required to complete A Favour for a Friend, head back to the woman and accept her Dinner Invitation. During the dialogues, you need to say all nice and romantic things and you’ll eventually end up inside a tower where the Achievement/Trophy will pop-up.
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