You can create a colony in Atlantis after you've explored the land and made the Infinity Trident.

⚠️ Be attentive: the Infinity Trident allows you to go to the past and explore the land once again. Do not activate it after you've completed Atlantis once if you want to make a colony. But if you do decide to do the land one or two more times, you'll get more rewards, new scrolls of choice, and absolutely any reward from the Star Forge.