You will be able to start Sherra’s sidequest by speaking with Amatsu at the Imperial Palace; he is not that far inside, at the bottom of the stairs, just inside the first door. He mentions that a prototype vulcosuit has been stolen, but there are no leads. As you attempt to exit the palace and go to the world map, you will be stopped by a Twilighter and your next stop will be Sacred Rahet. Enter through the main entrance and approach the elder to get another scene, this one being lengthy, and your next destination will be set, which is Mistral Gorge. Land your winger outside the eastern entrance/exit, save your game and make sure you health is full, as when you enter from this side, you will be pitted against the boss.
BOSS - Emperium 2
As the name of the boss suggests, this is a stronger version of the Emperium you fought in Dhaka Venu 2. If you remember, the main point of this boss is that it counters everything, so you’re going to take damage no matter, should you attack him. To make matters worse, the boss will likely use Amplify on its first turn, meaning its damage will be increased by a lot. Amplify will make its counter do upwards of 150 damage or so.
Remember to watch out for its Pierce, which only hits straight ahead, so you can easily avoid it by positioning your characters. By far, the most threatening skill is Annihilate, which does a lot of damage to the entire party, but it can also instantly KO them. If you can get through the battle without seeing this move, then you shouldn’t really have any trouble with this boss. You will want to hit hard and fast, so it’s best to keep your vulcosuits equipped from the beginning of the battle.
Once the boss is finished, watch the scene and then return to the elder in Sacred Rahet to get the War Maiden Spritnite. The sidequest will be officially be over at this point, but you can take that spritnite and get the Valkyrie skill spritnite at any magic consortium (you can also now create the same thing with memories).