Apprentice Clerval is a mage who is an apprentice at the Mage Training Arena. He seems relatively new to magic, he says that under pressure he can't perform magic too well and often accidentally casts the spell on himself. He has more of an interest in construction than magic. He is the starting point and the main NPC for Rune Mechanics. He can provide a new Rune guardian pet to players after this quest and is currently the only known source of a Rune guardian pet.
When getting a new Rune guardian, he doesn't ask for any more rune essence or pure essence, so he must have access to the essence mines or buy the essence himself. Or, like many reobtainable items, the rune guardian returns to him when you dismiss it.
The outfit he wears closely resembles and may have been the precursor of the Investigators outfit from the Cryptic Clue Fest II.