Whilst the ceremony is in progress, everything in the town is blocked off - including the Inn. The healer guy, however, isn't, but you'll need to reach him first. Thankfully, he's on the path you need to use to progress up to the Great Gabomba (the big statue thing you saw on the world map) anyway.
Before you continue on, check the jar in front of the old woman (left of the Weapon & Armor store) for a Lucky Pepper.
Outside of the actual town (but not onto the world map) there's a rope to Lash to the left-hand side. Climb up it and hop across the pillars. On the right-hand side, you can head all the way north to find the healer, so talk to him if you want. Hop across the pillars to the left of him until you reach the roof of a hut. Jump on the roof and then across to the ledge on the left. Head on north to the next area.
You'll enter a scene the moment you arrive here - Akafubu, a random guy wanting to become the new witch doctor of Kimbombo, is trying to please the Great Gabomba, so he can become it. The black orb is here, and you'll need to get it back. When you regain control of Felix, head up, and approach Piers. He'll be more than a bit puzzled that you followed him here to help him when you barely even knew him, but that quickly becomes irrelevant. Apparently, the fact that Akafubu can use Psynergy is surprising. Now, you'll have to help Piers by moving the pillar out of the way. Once you have, he'll talk with you again, and for the next few minutes or so, in quite possibly the least appropriate place, there'll be a discussion about Piers' home of Lemuria.
After this, Piers will join your party. Congratulations! You now have a complete party! For the mean time though you will have an abundance of Mercury Djinn. This can be remedied soon, but for the mean time, set to standby any extra Mercury Djinn so your characters retain their original classes. Carry on north, across the pillar. Whilst you're here, give Piers the Storm Brand. Climb down the vines. There's nothing in the random area to the top, so use Scoop on the cracked ground just below the vines to uncover a ladder. This leads to the Gabomba Statue.