Circumstances that will bring the party together

The Worldwound. Despite the best efforts of the citizens of Kenabres, and the multiple crusades led by the humans inhabiting the area, this terrifying crack on the surface of the world keeps on vomiting demons and other such atrocities, who corrupt and twist anything they can't outright destroy. Led by the terrifying Overlord Deskari, the demonic armies have now brought the fight to a whole new level, spreading a curse on the surface world.

Far away from the safety of Kenabres and its Wardstones, and dangerously close to the Worldwound, a small village exists. It is the village of Holt, and it is your hometown: all the experienced, combat-able adults in the town have been transformed into demons and monsters, and while they still retain their sentience and free will for the time being (by which I mean, even if your dad became a monster, he still acts like your dad usually would, and hasn't attempted to harm you in any way), they're unable to fight against the demonic armies, as the curse literally makes it impossible for them to rebel against the demons. You, the youngsters of the town, are the only ones still retaining your humanity.

Until one day the village's witch, who has retained most of her powers as a skilled conjurer despite the transformation, comes up with an idea: why not repay Overlord Deskari in kind? Much like he made it impossible, by using the curse, for the adults of the town to fight against the demons, the witch should be able to summon Deskari and bind him to your party via a summoning pact, thus making it impossible for him to fight against you. Literally the first scene of the game will be about the witch attempting the summoning ritual... But something goes wrong. Zany adventures ensue.