10 Times Your Unfinished Business In Video Games Caught Up With You
2. Don't Let Keira Go To Radovid - The Witcher 3
The Witcher 3 is mostly a linear experience. The choices you make have great consequences in the context of the missions you do, but they rarely have an impact on the overall story.
Rarely, but not never, and that's because missions like "For The Advancement Of Learning" exist.
In the quest you help Geralt's mage friend, Keira Metz, recover a cure for the Catriona plague, which caused thousands of deaths in the past.
When you finally find the notes about the cure, the sorceress reveals that she seeks to present them to King Radovid, in hopes of getting on his good side, after he began a nationwide hunt on all magic users.
The plan obviously sounds like suicide, so you get a chance to convince her to go to Kaer Morhen instead, but you can also shrug it off and let Keira do her thing.
Unfortunately, leaving Keira's fate in her own hands leads to her death. You and Triss find her remains shortly after she sets off to see Radovid, so if you don't want to lose a friendly mage, make sure you intervene in her plan while you still can.