Grapp Keep

1F

Walk straight ahead to trigger a scene. After that, follow the path west to find an X-Potion at the end of the path. Next, follow the available path to the east and pull the lever to open the gate to the immediate west. Go through that gate and head to the second floor.

2F

Open the chest to the south to get 2000pg then pull the lever to the north. Go downstairs using the stairs to the northwest.

1F

Pull another lever here to open yet another gate. Return to the second floor and backtrack again to the other stairs leading to 1F. Head north to the newly-opened gate and you'll find two chests inside the next hallway. One is locked blue chest while the other contains a Turbo Ether. Now take the stairs north of the keep's exit.

2F

This will trigger another apparition to appear. After that, continue north to find two set of stairs. Go downstairs first. That stairs should give you access to the enclosed chest in the first floor containing a Glaive. Return to the second floor and take the stairs to the left to reach the third floor.

3F

You'll see another apparition. Take the path leading southwest and you'll find a Rebuff Lock. After that, follow the path to the east and south to trigger another cutscene. After that, continue south until you reach the ladders going down to 2F. Before going down, enter through the secret passage to the right of the stairs going south then west to reach a chest containing an Elixir.

2F

Follow the path to the west until you find a lever. Pull it down to open the gate to the immediate right. Head to the east this time and loot the chest in the southeast corner to get a Bomb Fragment. Head north and enter the room to the left to find the last chest in the floor. Loot the Bacchus's Wine from it. Take go downstairs to the northeast afterward.

1F

Finally, pull the lever here to create a shortcut that leads outside the keep. Now head back to the stairs in the middle of this floor again. Once in 2F, go south to the newly-opened gate and go to the next floor.

3F

Save via the adventurer and prepare for a boss battle. In this battle, you don't need special preparations. You just need to boost your party's physical defenses. Once ready, head north and pick up the shining object on the shelf. A cutscene will trigger and a boss battle afterward.

Enemy: Automaton x3

HP: 10,000, Weakness: Lightning, FAM: Inorganic

Spam Thundara on these enemies and concentrate your single-attacks on a single-target. Their only means of attack is Rocket Punch that deals damage to all party members. Just keep constant healing until you win.

After the battle, head back to Eisen Bridge and hand over the sample to Commander Goodman. After the scene, talk to him again to start another sub-scenario. Select the third option to proceed with it. For the full walkthrough of the sub-scenario, follow this link.