Funnily enough, Simo (Card's character) made an interesting observation about the creature. Long story short, this will either be a reasonably quick Boss Battle or an arduous one. It all depends on where the characters decide to direct their attacks.

Quick trivia about the Guard Armor. In the games, focusing on the Torso (the head apparently counts as part of the torso somehow) will kill the Boss faster, but taking the time to destroy the limbs first will yield more Health/MP/Munny drops. Since the RP will not be using those kinds of metagame concepts, you can probably guess which strategy will be better.