Architect on Eos
The Architect on Eos can be found during the side mission Making an Impression. After placing the first two seismic hammers, Ryder will encounter the mechanical beast after activating the third.
Architect on Voeld
This Architect is found during the side mission Missing Scientists. It's found after you settle the outpost and complete the vault. Follow the trail of dead thinker to find this beast
Architect on Kadara
The Architect is found on the planet of Kadara after you've settled the outpost on the planet. Go to Christmas Jones at the top of the building complex and activate the Old Skinner quest.