Atlas:
The Atlas of Worlds is a visualization of the dream worlds that are opened by activating maps, indicating how these worlds are linked. The player starts at one of four starting maps in the center of the Atlas. These tier 1 maps start dropping on Act 8. Players can find new maps in adjacent, connected maps in the Atlas.
Map drops are not completely random; instead, a specific tier is chosen first and the map type is chosen from a pool of maps completed for that tier or connected to the map the character is currently in.
Region:
The Atlas is split into 8 different regions, each affecting a Watchstone or Conqueror's area of influence and what item bases can drop.
The 8 regions are:
Glennach Cairns
Haewark Hamlet
Lex Ejoris
Lex Proxima
Lira Arthain
New Vastir
Tirn's End
Valdo's Rest
Atlas Completion Bonus:
For each map completed under certain conditions, you gain an Atlas completion Bonus. Each Bonus adds a 1% chance for a map to drop one tier higher, with each 100% chance automatically upgrading the tier of the dropped map. The maximum map tier, however, cannot bypass drop restrictions, even if it would have been upgraded. (You can also buy POE currency online)
For example, a rare monster in a tier 6 map with 125% completion bonus:
a rare monster can drop tier +1 maps, as such it can drop tier 1 to 7 maps
it will only drop maps that are adjacent or already unlocked (completed) on the atlas
a tier 5 drop would be upgraded to tier 6, with a 25% chance to be upgraded to tier 7
a tier 6 drop would be upgraded to tier 7, but can't be upgraded any further
a tier 7 drop is already the highest possible drop, and can't be upgraded any further
Map Changes:
Map tiers and locations have been shuffled (though the 'pin' locations for maps has not changed). Most maps are now initially found at a different tier. Unique maps have not moved or changed tiers.
Improved signalling for advancing the Atlas questline step in which Zana opens a portal after the map boss is slain.
Penitentiary Incarcerator (boss of the Dungeon Map) will no longer spawn infinite Skeletons if he's allowed to live indefinitely.
Ancient Architect (boss of the Pier Map) will no longer summon spiked ground on top of other spiked ground.