Path of Exile's pre-launch patch a kitchen sink patch; this is big enough to include the sink, dishwasher, fridge, and probably a good chunk of the dining room besides. It's a big patch, and when it goes fully live tomorrow, you'll have a chance to play around with the enormous list of features, starting with the addition of an entire system for guilds that didn't exist before.
Yes, the patch includes a guild system. And that's not even the biggest part of the patch. It includes a new character class for players who have cleared the game on Normal difficulty, six new world areas, achievements, new skills, new items, and an assortment of balance tweaks and improvements. That's not even touching upon new challenge leagues and the like. The point is that even if you know the game inside and out, you might want to hop in tomorrow and try out the huge array of new options available to you because... really. There's lots of stuff here.