The Atlas of Worlds
The Map system is more than just a bunch of individual unrelated maps. Instead, the maps you'll find are part of a cohesive whole with a clear progression. Each map has a location on the Atlas of Worlds, and the locations of, and connections between, maps drive some of the endgame's major mechanics.
(The Atlas' arrangement changes with some patches, so the above image will not match your current Atlas. It's fundamentally the same type of structure, though.)
Low-tier maps are located at the four corners of the Atlas. As you progress, you'll move closer and closer to the center, where the higher-tier maps - and some of the final bosses of Path of Exile - can be found near the end of your character's progression.
Map Drop Mechanics
Maps cannot just drop in any zone - at least at first. Tier 1 maps, which you'll find steadily throughout the latter half of the main storyline (and which you no doubt have a stock of by now), are an exception.
Instead, when a map drops, it goes through the following sequence of steps:
First, the game determines the tier of the dropped map. This is rolled randomly from Tier 1 up to a maximum: Normal monsters can drop up to the tier of the current map, Magic and Rare monsters up to the tier of the current map +1, and map Bosses up to the current tier of the map +2. For example, if we are in a Tier 4 map, Normal mobs can drop maps from Tiers 1-4, Magic and Rare mobs from 1-5, and the Boss from 1-6. Subject to these caps, there is also a chance to raise the tier of your dropped map: for each bonus objective (see below) you've completed on the Atlas, you have a 1% chance to upgrade your map drops by a tier.
Second, the game determines which map of that tier will drop. Not all maps are eligible to be chosen: the game chooses from maps that either (a) you have already completed on the Atlas or (b) are connected on the Atlas to to the map you are currently in. If there are no eligible maps of the appropriate tier, the tier is dropped by 1 and this process is repeated. If there are still no eligible maps, the tier will drop by 2 and repeat again, and if this fails the drop will simply fail. This will almost never happen unless you are performing fairly extreme manipulation of your Atlas. Maps that are directly connected to the map you are in on the Atlas have a higher weighting, meaning they are more likely to drop than other maps of that tier, particularly if they are not yet complete on your Atlas.
The result of these mechanics is that you can, to some extent, control what Maps drop by controlling what you do or do not complete on the Atlas. This is an advanced technique called Atlas Manipulation, and is not covered as part of this guide.
Every type of map (e.g. Lookout Map, Beach Map, Lighthouse Map, etc.) has a Bonus Objective associated with it. These objectives, generally speaking, just involve running that type of map on some minimum difficulty:
- For white-tier (Tier 1-5) maps, you need to run a magic (blue) rarity version of the map.
- For yellow-tier (Tier 6-10) maps, you need to run a rare (yellow) rarity version of the map.
- For red-tier (Tier 11-16) maps, you need to run a Corrupted rare version of the map.
- For Unique maps, you generally just need to kill the boss.
Because these objectives grant bonuses to the tier of your map drops, you will almost always want to do them when possible. The only exception is if you are manipulating which maps are completed on your Atlas, in which case you might avoid running certain maps altogether.
Sextants are special currency items that can be used on the map types displayed on the Atlas. There are three types of Sextant, in colors corresponding to the tiers of map they can apply to.
When used, a Sextant applies a bonus effect to the targeted Map type and every other type within a small radius around it. This effect generally has 3 charges, and each time you run a map within the radius of the sextant, you'll consume one of these charges. Once the charges are gone, the sextant disappears.
Initially, you are limited to one sextant on the atlas. As you complete maps, you'll eventually unlock the ability to use more. Sextant effects can overlap, although only one sextant can be centered on any given map at a time.