- Speak to the commander. Your faithful companion Datz will take off, and the commander of the Shieldbearers will give you a new task: scouting out an enemy stronghold to the northeast.
- Return to the world map and you'll find the gate to the southeast of the Eisen Bridge to have opened up. Head through this and wander north.
- (Note also that after you open the gate you'll also unlock a side quest back at the House by the Sea. Something to do with a spooky ghost ship. Ooooooo.)
- Your next destination will stick out like a sore thumb as you wander north, no worries.
- Start by sweeping east and north from the entrance. There are a few dead ends up here, but the left-most accessible room has a switch to pull. Do so to open a door to the west.
- Return to the entrance and head straight north to hit a cut scene. You'll quickly get the sense of the kind of enemies in this place: largely undead.
- Head northwest through the first large hall to find a small offshoot hall. It leads to an X-Potion.
- Ignore the stairs for now and go north through the door you opened earlier. Northwest of here are stairs to go up.
- Second floor. Run south of the stairs to find a chest containing 2000 pg, then proceed north a short ways. You'll find a switch to pull on the right wall which will open a door nearby. Before rushing to it, continue north to find more stairs; they'll lead to a switch on the first floor which will open yet another door.
- Return to the first floor and go through the door to your immediate right at the bottom of the stairs. Inside you'll find a blue chest which you can't open and a normal chest containing a Turbo Ether.
- Return to the first hall in Grapp Keep and go up the stairs you avoided earlier.
- Second floor. A cut scene will trigger at the top.
- Run north. Up ahead you'll find two sets of stairs, one leading down and the other up. Go down to find a Glaive in a chest, then go up.
- Third floor. Another cut scene ahead. After it's done, run west and all the way south to find a chest. Inside is a Rebuff Locket.
- Return north and follow the eastern path to the south this time. Another cut scene will trigger. Looks like the bad guys are facing some disagreement in their ranks.
- Continue south. There's a robed save dude to your left, but you can ignore him for now and continue south. There's stairs ahead.
- Second floor. Go south and follow the path west to eventually find a switch which will open a door nearby.
- Return to the stairs. Sweep north to find two chests in separate rooms, the first containing a Bomb Fragment and the other Bacchus's Wine. Continue onward to the northern wall to find another set of stairs. These lead downstairs to the first level, where you can hit a switch and access the entrance / exit of Grapp Keep.
- Use the stairs in the first hall of Grapp Keep again. Go south through the door you just opened to the south and up the stairs you find. Robed save dude is waiting.
- Run north. Cut scene follows.
These things are painful hitters, but their weakness to thunder attacks can be exploited to bring them down in a hurry. Keep somebody on healing duty to cope with their all-hitting Rocket Punch attacks and focus on them one at a time. Not that bad a fight, really, so long as you don't let them boost their attack power. Shrug?
- All done. Return to the main map.