Path of Exile's Legion update is here, and it has some of the longest patch notes I've ever seen. The two most important changes are, firstly, that it adds a new Legion Challenge League in which you'll visit battlefields frozen in time, smash enemies to wake them up and collect a mountain of loot. Secondly, and perhaps more importantly, it includes the action-RPG's long-awaited melee overhaul, which should make whacking enemies in the face a lot more satisfying.
When you attack, you can now hit multiple targets by default—previously, the game would automatically choose a single target for you. You can now interrupt skill animations with movement or a movement skills, too. As long as you haven't dealt any damage with the skill you can instantly launch straight into a different one.
Your accuracy is no longer capped at 95%, which means enemies will be unable to avoid certain attacks. Enemies with shields can block attacks, but they'll just prevent a portion of the incoming damage, rather than all of it.
Animations should now be more fluid: a dual-wielder will "alternate attacks in a way that feels much more natural", making your off-hand weapon choice more important.
The way enemies attack has changed, too: instead of just locking onto you, they'll deal damage in a 120-degree arc in front of them, which means you can sidestep out of the way if you're fast enough. Enemies now have a slower attack windup, making it easier to respond with an appropriate movement or skill before you get hit.
For the Legion Challenge League, players will find monoliths in the world that they can activate to unfreeze ancient battlefields and defeat the newly-active soldiers. You'll earn "great rewards" from these soldiers, and you might even get a splinter, which you can combine into Emblems. Placing two or more Emblems in a map device will take you to the Domain of Timeless Conflict, where you'll battle some of the armies you've already faced, as well as new, powerful generals.
The update also adds a long list of skill gems, jewels and items, including Incubators, which will only reveal their contents when you've slain a certain number of monsters. If you're interested, check out the full patch notes here. You can click on the headings in the contents to read specific sections.