Behemoths are massive and are buglike in structure. They have two eyes and a large mouth which can spit fire. Their backs have a massive crystal-like structure on top of them, which features one massive crystal that glows orange. The entire body of a Behemoth is colored purplish-blue. Their armor is strong enough to resist hits from Silhouette Knights, although Ernesti manages to plunge his sword into one's leg, suggesting that their leg armor is far weaker than their body's. It is shown that their eyelids are highly resistant to swords, as a Silhouette Knight's sword glances off of one, leaving only a mark.