Mana

Mana is the type of energy used by mages, as well as what their bodies are made of. It is hundreds of times more potent than essence, and only gets more powerful the higher tier of law a mage is bound to. Mana itself is not the real resource, however. It is the byproduct of the connection between a cultivator and a law, and the real resource, spiritual energy, is not accessible until the S-Ranks.

Trivia

 * The name is apparently an abbreviation for Mercurial Apex-Neutral Asset