I found this hardcore social experiment server where you only get one life and then you are done. It runs on Java 1.21.1 and it also supports Bedrock so more people can join.
The world is split into two islands and they feel totally different. One is a winter wasteland that is harsh but packed with rare minerals and resources. The other is a summer island that is easier to live on but it can get super overpopulated.
Both sides share one global economy so the islands are still connected even if they are rivals. Simple Voice Chat is required for every interaction so you actually have to talk things out.
The whole event is run in weekend sessions so more people end up online at the same time and the power struggle gets intense.
