Expected to land in mid May, patch 0.2.0h is bringing private leagues, a feature from Path of Exile 1, into the sequel.
Private leagues are primarily a social feature, similar to guilds but with less permanence. Also, like creating or expanding a guild, they are a paid-only service. The pricing structure for POE2 isn't confirmed yet, but in POE1, they cost 6 MTX points (about USD 0.6) per player plus a small setup cost. They run 10 days by default but usually get run for longer (which adds a small cost).
Private leagues allow you to create a fresh start economy that neither characters nor existing stockpiled wealth transfers into - everyone starts fresh - but unlike a GGG-organised fresh league start, ONLY players that are invited into the league can play in it.
They are popular with three main groups in POE1. The partial implementation in POE2 doesn't offer anything for the second group... but that is coming in the future.
- Highly competitive players looking to have competitions on a game-enforced level playing field.
- Groups (or individuals) looking to play the base game but with extra mods to add difficulty. (In POE1, this includes modifiers like 'Monsters act 20% faster' , 'monster skills fire +2 projectiles' and 'Players have -40% to all resistances'. There's no protection against making a league that's too hard for anyone to ever complete.)
- Guilds or other social groups looking to play with each other, but nobody outside their group.
If you aren't interested in these use cases, you can entirely ignore that private leagues exist.