How to Progress the Atlas
Start with Low-Tier Maps:
Once you finish the campaign, you’ll begin finding T1–T5 maps. Start running these to fill out your Atlas.

Complete Map Objectives:
To «complete» a map and unlock progression, kill the boss. Doing so POE currency unlocks adjacent maps and adds them to your potential drop pool.

Unlock the Voidstones:
There are four Voidstones, earned by defeating powerful endgame bosses. Each Voidstone raises the base tier of maps on your Atlas, so you eventually only drop T16 maps.

Use Watchstones/Atlas Stones:
These stones allow you to POE 2 Currency unlock more challenging versions of maps and increase their item level. In PoE 2, this system is more streamlined but retains the core goal: scale up your content and loot.