Far Cry Primal

You will receive this after completion of the 3rd mission for Tensay the Shaman, or the 4th if you include the initial mission where you recruit him for your tribe. The mission is called 'The Take Wenja'.
Not a hard mission if you've got an upgrade or 2 on your weapons and health, if you're not very strong and have just gone straight into missions you may want to use a bit of stealth, as there are some elite enemies about. Once you have rescued all the captured Wenja at the 3 locations just go talk to them at the waypoint and the achievement will unlock.

If you're unsure what Tensay's mission icon is on the map here is a screenshot. I know the icon is small but it's the best I could do, still easy enough to see though and it's the only icon on there so should be helpful enough for the people that need it.