Items: Life Gem
You passed over it before because you were in a rush to get to Pimento Park, but now you have time to visit Star Ridge. As Parin enters, you'll witness a video in which she confronts Prince. He denies being the doppelganger (which makes sense, as the one who stole your identity is obviously Cream) and refuses to release Pino. Her captivity is for her own good, he claims. Then he fires smoke in Parin's face and escapes while she's busy coughing.
When the smoke clears, there's a platform to step onto. Once Parin does, it will transport her to the other side of a gap, where she will confront Cream. The female Phantom goes through several shapes before settling on the default, a clone of Parin. Now it's time for a boss battle.
Boss Battle: Cream
First, make sure you're wearing something useful like the high-level Monkey Hat or the Vampire Hat. Cream is a tough adversary. You'll also want to have plenty of chocolate with you, and cookies and shortcake. Your inventory should be full of those by now, since this is the first real challenge the game has thrown at you.
Because she is a doppelganger, Cream will be tough to ferret out. Start by using Energy Oil to preserve your drill's energy (otherwise the fight will be even rougher) and then you can focus on Cream. She is invincible when she takes your shape, so run around and avoid her attacks during that time while countering only with Drill Tornado moves. When she takes the shape of Cream--the white-robed girl with blue hair--that's when you can harm her. Move in at that point and do whatever damage you can with launch attacks, like you would on the other bosses.
Partway through the battle, she'll decide that one figure isn't of much use to her, and will clone herself. When you're doing damage easily to an enemy that looks like you, that's when you know you're focusing on the wrong target. It also means you probably have your back to the real threat, who by then is probably hurling fireballs around like there's no tomorrow. Try to find the true Cream and keep her in your sights at all times so that you'll be close by when she again takes on her true identity and is vulnerable.
Also, watch your life meter. You should be able to take some abuse, certainly, but this is a long battle and you will most likely be nibbling on treats fairly often. Any time you get down near around 15HP, it's time to start using curative items. Save the shortcake for emergencies, of course. Chocolate is probably the most useful, though the three cookies you can carry might also come in handy. Keep at it. This battle is winnable.
When the battle ends, you'll ask Cream why she's doing what she's doing and tell her that the Prince doesn't really intend to rebuild the Phantom Kingdom. She doesn't believe you, but there's not much time to argue. A rocket will blast through and take Cream with it. She falls over the edge and into a pit and wonders aloud why the prince would be doing this as she falls. The real prince would never behave like this, she thinks.
Grab the LIFE GEM
and you'll be prompted to save. Do so, then return to Monster Village. There, you can talk to the monsters to learn a little bit about a huge boulder that had once appeared at the entrance to Eggplant Caverns. Now it's gone. Puku, meanwhile, is nowhere in sight. Neither are the moles or Pecky, for that matter. Head to Tiese Town and you can talk to your grandfather, who reminisces about a childhood friend he can't possibly meet again. Go ahead and trade in more medals if you have any. Also, you might want to stop by the bakery to restock. If you do, remember to wear the crown for your discount. It will save you a few hundred, since Fan has jacked up the price of her treats yet again. Everyone still thinks you're guilty. When that matter is tended to, head back to Monster Village and save if it suits you, then head to the next dungeon.
NEXT: Radish Woods: Serpent Road