Nina’s fragile appearance and inability to speak may make her seem like a foe that even a random villager could defeat, but within her frail shell likes a mage of great power. With the ability to cast a variety of elemental spells, stat breaks, and most importantly, instant death spells, Nina is a dueller that many should fear. Since her ID is non-typed, Koromaru should likely find himself without any protection. Of course, even without it, her superior speed, ability to cut magical damage with equipment, and powerful spells should prove the pup’s downfall with or without instant death.
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In a battle of death versus death, usually the faster one wins. However, this fight will prove a nice exception: wonder dog Koromaru's immunity to dark-typed attacks may prove very useful here, as magical Death skills - such as Nina's - are usually tied to the blackest arts. As such, the versatile SEES dog will have an easy time around: he can either just burn the silent magician with Agidyne or leisurely cast his own death spells, which Nina has no protection against. Either way he chooses, Koromaru can easily bring yet another victory to his Shadow-hunting colleagues in the Duelling League!
SageAcrin And so, the pure power of ressucitating the undead has defeated Koromaru.
Wait, how does that work again?
Well, let's get this straight.
First, Koromaru is a dog posessed of a hellhound. Nay, the mightiest of them.
Hellhounds are demons.
Demons have a great power over the undead.
But how can you have a great power over the undead unless you truly understand them?
Certainly, the keeper of the gates of hell could be said to be, not only a demon, but undead himself.
But then, there are few that can truly be called a demon and undead, are there not?
True enough.
Therefore, Koromaru must be either a vampire or a lich. (Why those? Well, who else could you really see, out of the undead, someone calling a demon? A ghoul? Pff. Zombies? Hah. Skeletons? No.)
Since Koromaru is not, in fact, Godlike, however, those options are out.
Therefore, Koromaru is some form of drat powergaming half-vampire or something ridiculous like that.