All Tallnecks in Horizon Forbidden West

Desolate Lands (Scarlet Sands)

You will find the first one in the Desolate Lands. Follow the marker as Lawan will automatically tell you about machine. Upon arrival, inspect the generator under the station. After killing the enemies, shoot the mount and go up the two ladders. To the right of the data carrier, there is a third staircase leading down. Drop down and climb to the right to find the battery. After taking it, jump down and insert it into the generator. Climb one ladder and activate the console. Jump over the ledges to the left to find two cables. Shoot at their weak spots (look with the scanner) to turn the antenna.

Climb to the top, from the extreme point, jump in the direction of Tallneck and do not forget to open the shield-wing, holding the "square". This will activate your first Tallneck.