“Recruit all available companions.” ― There are 11 companions available in the main campaign, and they all need to get recruited. Since some could potentially be missed by rushing the main story, here’s a list of who you need and when they are available:
• Linzi and Amiri (they will stick with you after the Prologue).
• Valerie, Harrim, and Jaethal (the one that best fits your playstyle will stay after the Prologue, the other two will leave, but no worries. You can persuade one of the two to join your group at the Ancient Tomb in Chapter 1, and free the last one by talking to Chief Sootscale at the Old Sycamore while tracking Tartuccio.
• Tristian (meet him at the Temple of the Elk during Chapter 1).
• Octavia and Regongar (both at the Technic League Encampment in Chapter 1).
• Jubilost (Ford Across Skunk River in Chapter 2, can potentially be missed).
• Ekundayo (at the Ruined Watchtower in Chapter 2).
• Nok-Nok (found at the Goblin Village in Chapter 3).
The DLC exclusive companions don’t contribute towards the completion of this achievement.