Vulcans cannot be hit with Physical attacks while dormant, always dodging them, unless the attacker is Momo equipped with Ice Chrysm. They are weak to both Frost and Earth, so moves like Iceblast and Quake are very effective.
Vulcans are some of the best monsters for grinding, as when struck with a Flame spell like Burn, or even just a Molotov, they will awaken and attack. This boosts their EXP gain to 900 (300 per character), as well as gives the chance to learn Lavaburst. When combined with an Ivory Dice this can create a massive EXP gain for easy leveling. Even later game monsters like GooTitans don't offer as much EXP as an awakened Vulcan, making them prime targets for quick and easy grinding. Stealing the Protein is also a good idea, as it can be stolen either before or after it's awakened, and makes it an easy supplier of the Defense-boosting item.