- This chapter begins on a sour high note. Once you gain control you’ll be operating the Jester, a jolly, oblivious fellow. There are lots of people in the courtyard where you meet the guy, though ultimately you just have to have a look at the various tableaus underway. Check out all six, then head north and into the Castle.

- The throne room’s next. There are plenty of people inside, but you only have to speak to the king and queen in the north. Leave again once you’re done chatting to trigger another cut scene that will kick the heroes out of your party. For once you’ll have two other characters in your party, namely Guard I and Guard II. So exciting.

The Magical Maze of Anti-Intrusion in OH! RPG!.
The king... he has issues.
Magical Maze of Anti-Intrusion

- You’re now in a ridiculous maze. The prison you need to reach is in the southwest, but you can find some other things in here as well, if you’re willing to explore. The majority of them are upgrade items for your three characters - and, yes, you should also upgrade the two Guards.
  • Head to the northeast and you can find some Steel Ore in a chest.
  • There’s more Steel Ore in the southeast.
  • Chests in the south contain a Sharpening Plate, a Steel Ore, and a Red Bow.
  • Just outside Harold’s room in the west is a Sharpening Plate.
  • Chests in the west / southwest contain Steel Ore and a Sharpening Plate. Further southwest, in the very corner of the area, is Steel Ore and a Sharpening Plate. Near the Sharpening Plate are the stairs to the prison.
- Check the southwest corner of the prison for a Stimulant, the south for a Potion, and the southeast for stairs leading back into the maze; this last area contains a Potion and two Heavy Bars. Then head north and check the northeast corner for a Potion and an Ether and the northern room with the caped dude for a Stimulant. Said caped dude is the Captain you were sent to find.

- Leave the prison and head north through the Maze. In the northwest corner you’ll find a solitary wooden door. Your next foe is inside…

Harold, reduced (or elevated?) to a boss in OH! RPG!.
You knew you'd have to fight one of them.
Harold

Yow. As tough as can be expected. Harold is strictly a physical fighter, and he uses several melee blows to quickly whittle down your team’s power. Harold’s normal attack is puny, but his special strikes are absolutely brutal. The epitome of this is Sword Dance, which hits everyone for around 1,000 HP each. Yikes. At full strength that’s insta-death for your whole party. 

The only way to survive is to lower Harold’s attack power and then prevent him from attacking as much as possible, and that means using your magic. The Jester himself is the best at this, as Colorful Pop! greatly reduces Harold’s attacking power and Confetti Swirl can confuse him into hitting himself. Your other teammates have some good special attacks, too, though the only one you should absolutely get out is the Captain’s Edge of Steel, which will eat away at Harold’s defence. Use Potions to heal occasionally and Harold shouldn’t bother you too much.

Escape

Bad things start to happen at this point, and you need to rush to Harold and escape from the Castle. You have nine minutes with which to do this, and unfortunately there are things you can pick up along the way that could be of some use to you. You can find the following in the Castle:
  • A Hi-Ether and an Ether in Therese’s room - don’t check the book, however
  • A Potion and a Heavy Bar halfway up the Princess’ Tower - to get here you need to ascend via the outer wall, then go up the stairs at the bottom until rubble forces you from climbing any higher
  • The items you didn’t collect earlier are still available, though they’re now protected, so hopefully you got them earlier
Once you reach the Maze you’ll start running into creatures called Kalikos. They’re moderately powerful opponents that are better at stalling you than killing you outright, through their Tornado attack can one-hit you if you aren’t careful enough. Balloon Trick is a great way to quickly blow through them, as is Call Ralph!. If you don’t want to fight, don’t move until they turn around. You can get Smelly Fish and Stardust by killing Kalikos.

- Run to the northwest corner of the prison once you make your way there. You’ll find a chest containing a Potion and a shelf with a Prison Key. You can use the Key to open Harold’s cell, to the east of the room with the Key. Doing so will take you out of the Castle, into a cut scene, and, ultimately, into a boss battle. Or, if you want to get into an optional battle first…

Kalabhii, a side boss in OH! RPG!'s final chapter.
Final-ish chapter. Penultimate chapter.
Side Quest - Kalabhii

In order to trigger the small side quest of this chapter you need to speak to Harold, learn about the fire witch that’s attacking people, and then run over to fight her. Kalabhii is no big deal - she’s honestly easier than the Kalikos you were just fighting. Use Confetti Whirl right off the bat to confuse Kalabhii, then smack her one. Keep it up, confusing her as necessary, until she goes down. Side quest complete!

As for that final battle...

The King, final boss of OH! RPG!.
Giant Space Flea From Nowhere? Not quite, but bordering on the trope...
The King

Looks like an appropriate end game boss, doesn’t he? The King is much more a nuisance than an outright threat. He prefers status attacks to smashing you down with overwhelming force, and will try to crush you by outlasting you rather than just stepping on your poor Jester. He’s capable of raising his defences to nigh-impregnable levels with Soul Shield, can Paralyze you so you miss turns, and at least tries to heal himself… though you get healed instead, which is nice. The King’s most powerful attacks are Everflow and Righteous Ruination, which, though rare, will both kill you in one move. There’s no predicting when The King will use either one, making prediction rather irritating. Despite that, it’s not a terribly difficult fight, though it may take a while. Your options:
  • Hero Call! You only have Therese, but she’s more than enough. The key here is to keep The King disoriented with Confetti Whirl, then smack him whenever you get a spare moment. Therese jumps in to heal you with Prayer, provide extra defence (not really necessary) with Cover, and, most important, bust up The King’s Soul Shield with Shield Break. 
  • If you decide to go for full points and leave Therese out you’ll need to keep The King disoriented with Confetti Whirl at all times. Colorful Pop! keeps his attack strength low enough to be negligible, and Swoosh! will grant you extra TP per turn while allowing you to avoid his attacks all the more. If you’re feeling especially gutsy you can forego Colorful Pop! and just wait for The King to hit himself, which will do a fair amount of damage. The battle’s riskier this way, but it also takes a lot less time than doing the damage yourself. Just be careful not to use Balloon Strike more than once in a row, as The King usually seems to retaliate with insta-kill, even if he was previously confused.
Once you whittle The King’s health down once you’ll receive the option to Call Harold. Hold out for four more turns after doing so to end the fight, and, past that, the story itself. (More or less, anyway.) Congrats! Now, as for those little cheats you've been collecting...