The Legacy of Phrecia event will feature a new system for specialising in endgame content, replacing the existing Atlas Passive Skill Tree. As you progress through the endgame you'll find Idols, which can be placed into a new tab on the Map Receptacle UI to modify your maps.
Magic Idols can have up to two modifiers, Rare Idols can have up to four modifiers, and there are Unique Idols for Keystones from the Atlas Passive Skill Tree. Idols are tradeable but they are not modifiable.
This is a pretty drastic change to how the Endgame will play given the Atlas Tree has been such a fundamental part of the Endgame for some time, in many different formats and versions.
One of the major changes is that it turns specializing into different leagues to be less deterministic because it relies on you finding items. On the other hand it adds a layer of excitement to item drops in the Endgame not previously there.
This allows you to have an infinite number of different Endgame loadouts for content, no more respeccing your Tree at all, now just take out the Idols you don't want, and put in the ones you do. You'll probably end up with a set of Idols for each league.
With the Atlas Tree, you can only get so much of a given stat because that's how much we put on the tree, but with this system you can get a lot more of certain things pushing limits and boundaries further than ever. For example, if you want to have all Essences on monsters be at the highest possible tier, or a much higher number of Blueprints you find to be fully revealed
Given that this is an opportunity for us to let you play with more developmental concepts you can rest assured you'll find a bunch of broken outcomes in true Path of Exile fashion.
Full disclosure, due to these features being experimental for this event we haven't done the layers of Quality of Life that we would normally try to do to accompany it. For example you would want different inventories for different league sets or loadouts but instead during this event you will simply have to do the inventory management yourself. Based on the popularity of this system we can add more of these features in the future to streamline it to minimize item micro-management.
Given that players afterwards will likely want to experiment with the Ascendancy Classes or the alternate Endgame mechanic individually, we will be adding both of these as Private League options some time after the event.
We'll be posting the full details of the Legacy of Phrecia event later this week and will be teasing some more of the event Ascendancies in the meantime. If you missed them, the teasers can be found here.