This achievement is easily missable. Once you finish Main Quest: Ugly Baby the Secondary Quest: Brothers in Arms will automatically begin.
The quest sends you to collect allies. Each ally you collect is tied to a quest which you must complete in order to send them to Kaer Morhen to help in the battle. You must complete the quest and convince them to go. The Allies and their Quests:
- Keira Metz – Keira’s Cottage (Fyke Island): complete An Invitation from Keira Metz, A Favor for a Friend and For the Advancement of Learning Sidequests for her. If you killed her, you can’t get this Achievement!
- Vernan Roche – Temeria Partisan Hideout (near Novigard): complete Secondary Quest An Eye for an Eye
- Zolton Chivay – Rosemary and Thyme (in Novigrad): no Quest needed
- Triss Merigold – Triss’ Townhouse (Novigrad): complete Main Quest Now or Never
- Hjalmar an Craite – Kaer Trolde (Skellige): complete Secondary Quests: The Lord of Undvik, King’s Gambit and Coronation.
- Ermion – Kaer Trolde (Skellige): no Quest needed
- Folan and Vigi – Go with Hjalmar (Skellige): complete Secondary Quest: The Lord of Undvik and save each of them
You may miss some of the Quests, because of your Choises in the Game:
– You could end up killing Keira Metz if you make wrong Dialog choices at the end of her subplot
– If you choose the third Dialog choice during the King’s Gambit quest of the Kingmaker subplot you will walk away and neither Hjalmar, nor Cerys will become ruler. Then Hjalmar cannot be recruited anymore.
– You could ignore the Brothers in Arms story quests entirely and go directly to the Isle of Mists, thus missing all possible allies