Klantorr Island is, on the surface, not very interesting - too stable, rigid and peaceful for adventurers to fit in - and many clerics of the theocracy would readily agree. Nonetheless, things do happen that the Theocracy is not prepared for and adventurers are better-suited to dealing with.
1) The PCs are accused of sorcery and chaos-worship by a cleric and several townsfolk. The PCs can either try to run from overzealous soldiers, junior clerics and townsfolk, or try to prove their innocence to a higher-ranking cleric, preferably a sane one. The problem is caused by a mischievous mage who has found a spell that tampers with dreams, allowing him to make people dream whatever he wants them to. Among faithful folk like those of Klantorr, this can easily be misinterpreted as divine guidance. The PCs have a slight advantage in that they are not the first to be framed, and there are several suspects in the town jail who have been set up by fraudulent dreams.
2) A senior cleric in Berranport is actually a chaos-worshipping cultist with an amulet of non-detection. He seeks to create a Chaos Portal underneath Berranport in its sewers, and he believes the ritual to do this requires a number of human sacrifices. Although a proper Chaos Portal is well beyond his means, he has been contacted by creatures from the Planes of Chaos and has summoned some of them into his lair in the sewers. These have been used to kidnap certain townsfolk in Berranport and take them down into the lair ready for sacrifice. The chief cleric of Berranport is eager to stop these monstrous kidnappings, while his newly-appointed deacon (the chaotic cultist) will happily give advice that will steer the party into all manner of dead ends and wild goose chases.
3) The miners in the Valhorrian Heights have dug into a network of caverns connected to the Underworld, and troglodytes and grey goblins are causing havoc in the mines. This has put a dent in the local economy, and merchants are looking for mercenaries and adventurers willing to go in and make the mines safe. A band of five miners were captured by goblins in the initial battle, and they have been taken into slavery. Any captured goblin can tell the PCs that slaves are usually held for a while at an outpost near the surface before being taken down into the bowels of the Underworld - perhaps the PCs could rescue the miners?
4) A caravan of merchants and pilgrims travelling from Guntharn to Charventown have a doppelganger in their midst. As the caravan progresses the PCs and others notice that people have gone missing or turn up dead. In some cases this seems impossible as someone else was talking to the murdered person at the same time as others discover their corpse. It is a race against time to find out who the doppelganger is impersonating now, and to stop it before more people are killed.