All three of these are rewards for completing the "The Age Makers" side mission that comes the DLC, so you cannot unlock this achievement without first unlocking
Once you have completed the side mission, go to a base camp and equip the Oathtaker's Bow - Eternal Sentinel
bow and the Sinchi Chiqa Battle Dress - Honor Guard
outfit. Note that both of these are variations on similarly named items that were bundled with the DLC, so be sure that you are equipping these exact items, not their more vanilla counterparts. You learned the A Thousand Eyes skill at the challenge tomb, so you don't have to do anything at the base camp to make it happen. If you need to check this, press
from the Skills menu at the base camp.
EDIT: Fast travel to a base camp outside of the Hidden City to equip the outfit.
Once you have equipped the bow and outfit and exit the base camp, the achievement will unlock.