In order to complete Relic Ruins: Isle of Spires in Horizon Forbidden West, you need to find and enter a 7-digit door code to access the Ornament inside the locked room. You will need to explore the whole ruin and complete various puzzles to find all the parts of the code you need.
Climb the pillar in the middle of the flooded ruin, then use your grapple to get up to the higher floor. Use your grapple to get up to a higher floor still, then jump from the end of the yellow beam and use your grapple in mid-air to get to the east side of the ruin. Look back across, and you’ll see a crate. Use your pullcaster to pull it into the water below, then drop down after it.
Climb out of the water onto the floor east of the crate, then use your pullcaster to pull the crate out of the water. Drag it under the hatch, then use your pullcaster to open the hatch, climb onto the crate, and then climb up through the hatch. Crawl out of the vent, then climb onto the floor above it. Go through the gap to the south and use your Focus to read the Locked In! Datapoint. It tells you to start with a 2, then just hit each number counter-clockwise, which means the code is 2109. Go back into the room to the north and use that code to open the door.
To find the second part of the code, start at the campfire outside the northeast corner of the ruin. Climb up the outside wall, head west into the building, and go around the corner past the cylindrical device marked with a battery icon (it’s a charger, but not the charger you need to use). Use your pullcaster to open the ceiling hatch and climb up. Drop down into the room at the other end of the vent, and ignite the Firegleam.
Go out through the hole, turn left and left again, and remove the glowing energy cell from the wall. Take it back into the Firegleam room and place it in the charger. Wait for it to charge, then remove it and take it to the elevator on the east side of the floor. Power up the elevator, then ride it down to the bottom floor. Use your Pullcaster to get the crate out of the water, and drag it into the elevator. Ride the elevator back up, then drag the crate to the position in the screenshot below. Climb up to the ledge, then jump across to the other building.
Go through the gap in the wall into the office to the south. Use your Focus on the datapad on the desk, and it’ll tell you that the entry code to the office block is 1 – 0 – floor number. The title of the Datapoint is 9th Floor Security Measures, so the code for the door in this room is 1 – 0 – 9 (it’s also the second part of the code you need to get the Ornament). Enter 109 into the console in this room to open the door.
You now have both parts of the Isle of Spires Relic Ruins door code, which is 2109109.