Aeternum

Players start by choosing a first class from a class table, which gives a starting ability set and custom items such as swordsman longswords or rogue daggers. Each class can be leveled up, and after reaching level 10 the player may switch to another class through class stones, using a GUI. The catalog lists over 400 abilities across 16 classes, and an energy system and level-up system govern their use.

A merchant can be summoned with a function command. It sells class scrolls and class stones and has a 60% chance of replacing a wandering trader at spawn. By default the merchant glows and makes a sound for players within 30 blocks, and a config option changes or silences this. A trader totem drops when the merchant dies, and a spawn egg summons another merchant anywhere.

Aeternum is server required and client optional, so the server must run it while players may leave it out. Files cover 1.21.2, 1.21.3 and 1.21.4 for Fabric, Forge, NeoForge and Quilt, and the data pack form is also listed. The mod is released under the Creative Commons Attribution Non Commercial No Derivatives 4.0 license and is not open source.