Travel to the location of the Banuk camp marked on your map and speak to the Banuk tribe members.
Once you've spoken to all the Banuk, head on over to the shrine at the very back of the camp. Look to the left of it and you will find a path that you may climb on. Follow that path and you'll find some Oseram members messing with an artifact.
Examine the Artifact
The artifact is the source of the signal that's keeping the machines docile. Convince the Oseram to leave it alone and then examine the artifact.
Head back down the Banuk camp to discover that the machines have already begun to attack. Help the Banuk defend and kill the machines. Afterwards speak with Tikuk and return to Vilgund to report about your findings.
Banuk Artifact : Punishment (OPTIONAL)
Before you leave the camp, you can find a Banuk Artifact at the top of a cliff located near the entrance to the camp. Climb to the side where the writings on the mountain are prominent. It should be on the right if you are coming towards the camp and at the top you should find a Banuk Artifact to sell to a merchant for special gear.