Returning played for Atlas

Hey guys.

I tried using the search feature but it wasn't much help. I'm a returning PoE player looking to start back up once that Atlas leagues start back up. I played all the way back up through Tempest/Warbands, then had to quit for a variety of reasons.

Anyway, I'm looking to get back into PoE, and was wondering if someone could fill me in on he biggest/most important changes to the game in the past year. I've done my best to go through the wiki and old reddit posts, but the information is generally either not very detailed or too dispersed and hard to piece together.

Any help would be appreciated, thanks!