Relating to or of the nature of an arcanum or secret; mysterious or esoteric in character.
From arcanum + -al suffix (forming adjectives). It's a rare term that emphasizes the secretive or mysterious qualities implied by arcanum.
Arcanal is such a rare word that most dictionaries don't even include it—it's a word that exists mostly in very specialized occult or academic writing, making it itself rather arcane in the truest sense.
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