Ni no Kuni walkthrough, Part Thirty-Nine: The Vault of Tears
A trip to Glittering Grotto behind them, Oliver and his friends are off to find the second Magic Stone that will make Mornstar into a complete, potent wizarding weapon. His next stop on his trip is to the Vault of Tears, a mansion set into the forest west of Shipwreck Shore.
You've had many chances up to this point to explore Shipwreck Shore, and if you completed The Alchemist Brothers side quest then you've already been here. The monsters in these parts were previously too difficult to tackle - but now, after all you've seen, you should be ready to fight them.
Enter the ruins. Save at the waystone and check out the glowing green rune on the floor. It's of no use just yet, so ignore it and head down the stairs to the north. At the bottom you'll come across a statue of the Snake King who rules these ruins -
- and it will turn everyone into frogs. Oh joy. Everyone will spot a rainbow-coloured frog in the distance; better chase after it. Hop. Whatever. Your familiars are fine, at least, so battling won't be a problem.
(In case you were wondering, the green circle at the top of the stairs will turn the team back into humans… though the statue will re-frog you every time you descend the stairs again. Sigh.)
You can't do a whole lot as a frog, so take the path east past the statue. Follow the rainbow frog through the ruins, ignoring the side paths. It will lead you on a merry chase - to a green circle! Back to normal. Handy, that. Time to search!
Open the chest near the circle for an Espresso, then go west. You'll go in a loop that leads back to the snake statue room. (Avoid the statue's gaze or you'll have to do that whole thing again.) Head east through here to find another large, square room; in the southeast corner of the walkways is a blue chest with a Pie on the Bone. South of here is a nix trap, but if you're willing to brave it you'll find a Vial of Sage's Secret.
Run back to the second magic circle and go north. The rainbow frog is waiting, and it will implore you to help 'him' if you use Nature's Tongue. Who? It doesn't say. The way west is locked, leaving you no choice but north. You'll descend into a small dungeon, and in one of the cells is a big, talking frog. Save at the waypoint here and use Spring Lock to open the frog's cell. Esther will regale everyone with the story of the Frog Prince Ali, which is, supposedly, this man. He's been imprisoned by a great serpent named Aapep, which was brought back by… well, you know who.
Take Prince Ali to the magic circle nearby. Predictably enough, it does nothing. Ali will nevertheless vow to take you to Aapep; time to get a move on.
Follow Ali north. He'll take you to a room with nine niches in the floor, eight of them bearing images of frogs. Listen to Ali's hint, check his cell for the rest of it, then stand in the middle of the room and use Puppet String. This puzzle is almost annoyingly simple - just swap the positions of the two statues flanking the door. Ignore the squares around the room completely.
This doesn't open the door, but it does lower the water in the previous room. Run back east and go down the stairs to enter the former water pit. On the east side of the room is a purple chest; behind the grating in the north is a green chest with a Set of Storm Serpent Scales; hidden under the northern platform is a blue chest protected by a nix trap. Wait for the trap to wear off and you can open the chest to get the Serpent Key, which is probably important. Before you leave, get up on the southern platform and cross the stepping stones to your left to find a path to a Green Man's Cloak.
Return to the massive door, save your progress at the waystone, and use the Serpent Key on the lock. Ahead is a proper massive room… and when you approach the middle, the Magic Stone you're looking for will fall into the hands of massive Aapep, King of Cobras.
Aapep's not too tough. Most of his moves are just straight hitting affairs, though watch out for the all-encompassing Death Rattle, which also includes a dose of confusion to anyone who fails to Defend. Hack away at Aapep with fire attacks (you should have some of those if you already went to Yule) and heal up whenever necessary. Drippy suggests putting something 'heavy' on Aapep to stun the beast, but the spell of choice - Burden - works so seldom that it's not really worth the wasted MP. Stick to conventional attacks and bring Aapep down.
Aapep will vanish after the fight, leaving the Moonstone behind. Ali's story will end happily, and the group can get on with finding the third magic stone. (You'll also gain the story The Bear-Man and the Princess's Tears for your Wizard's Companion.)