Inspired from Re:Zero, this mod adds the Return By Death curse directly from the Anime.
The mod is completely server-side apart from the sound effect, which can be installed on the client via this texture pack.
The curse is automatically applied to every player in-game. Although, this can be disabled from the config, and then any mod which depends on this can enable it on various events in-game.
Randomly (can be disabled through config, so that dependent mods can implement their custom event), the world will save itself in another folder. When a player affected by the curse dies, the world moves back all the way to the last save. This also works in multiplayer, but the backup is not unique for each player. This means that if you're doing something and someone else dies, you will get teleported back in time as-well.