Nergal manages to get the gate open before dying, and three fire dragons crawl forth with a vengance. Ninian is revived by Braimond and defeats two of the dragons before her power is exhausted. You must defeat the final dragon on your own. I think the fire dragons look cool with their wings made of fire.
The dragon is so huge that it can't be contained on the screen. These are no wyverns, I can assure you.
These are the dragon's stats. It's an incredibly formidable foe, as you can see. Its attack, Flametongue, has a three-space range, like the Longbow. Pure Water and any other temporary ways to increase your defenses are useless against its attack. Its HP is around 100 or so. You'll need to take it down as fast as possible.
