The Isu Armor is a Secret Outfit in Assassin’s Creed Origins, obtained from the Great Sphinx of Giza after finding all Stone Circles and Getting 50 Silica from Ancient Tombs.
You can get the Isu Aromor at any point in the game after doing the main quests in Siwa (starting region). After Siwa the entire map opens up for exploration.
Step 1: Get the 12 Stone Circle Collectibles. This will open a secret room in the Great Sphinx of Giza.
See Stone Circle Locations Guide.
Step 2: Get 50 Silica (yellow glowing stones) from tombs. Each tomb has a few of them. There are more than 50 of in the game. The tombs have at least 80 Silica. They have fixed locations. The 50 Silica can then be traded for the Isu Armor inside the Sphinx (you only get access to the necessary room after finding the Stone Circles).
See Tomb Locations / Silica Guide.
Step 3: In the Great Sphinx of Giza you can interact with a big console after finding all stone circles. Then in the hidden room you can trade 50 Silica for the Isu Armor. The Sphinx is marked on the map as a tomb called “Eesfet Oon-m’Aa Poo” or as a questiion mark if you haven’t discovered it yet. It’s in the Giza region. Upon placing 50 Silica in the ancient mechanism at the end of the Sphinx, you receive the outfit.
It’s only a cosmetic item and does not affect any of your stats. It doesn’t provide special boosts or abilities, just looks cool.
You also have to do all of this for the trophy / achievement “Old Habits” which is for completing every location.
If you don’t have enough Silica you can return to previously completed Tombs to pick up the Silica you have missed. You can go back in all tombs.
Isu Armor Showcase & Video Guide