If you want to level up your minions, you need other minions.

Minions' bodies are made entirely of Aether, so they level up when the Aether concentration increases.

Once a minion has advanced to a sufficient level, you can use Minionite to begin evolution.

Minionite refines the Aether in a minion. This is indicated by a wing-shaped rune.

The more runes a minion has, the stronger it will be.

But please remember that certain minions cannot level up or evolve.