Levels MC

Plugin for PaperMC Minecraft servers that overhauls XP levels

Download

Every 10 levels, you gain an extra heart, up to 20 hearts by default
Commands to extract XP, 250XP per 10 levels you sacrifice above level 20 by default
Transfer XP directly to other people

Have a PaperMC server set up. For guidance on setting up the server, go to the PaperMC Documentation
Download the plugin from one of the Download Links above
Put the plugin in the plugins folder
This plugin only works client side. 300 downloads and I'll make a client-side mod.

When a player gets to 10 levels, they gain an extra heart. This continues every 10 levels until the player reaches the maximum, which is 20 by default
The heart count should update automatically, but if it's stuck, players can run /refresh to update their heart count
Players can run /extract to extract XP levels to XP bottles, at an exchange rate of 3 bottles per level. This can only be done when the player is at level 10 or higher, and the extraction doesn't bring the player to below 9 levels