I don't know the voice acting in KQ8 is all fairly tongue and cheek and goofy (with exception of Connor who comes off sounding 'over-dramatic'). Most of the characters once you step out of the first world start to turn towards more whimsical nature. Infact I'd say that most of the characters you encounter in DOD, are a bit more whimsical compared to those you encounter in the Realm of the Dead in KQ6 (with the exception of the dancing skeletons)... Even the enemies in DOD have alot of whimiscal 'threat' messages.
The game also starts to 'lighten' up visually once you leave DOD. Although scenic graphics were the product of the limitations of the time, and not very detailed by today's standards. It's that limitation that adds to a sort of dreariness to the atmosphere.
Other characters in KQ8 were pulled right out of the KQ list of archtypes really. Ice Queens, Unicorns, Beasts, crystal dragons, Witches, etc (several more fantasy than fairy tale, or perhaps legendary or mythological). Of course KQ5 pretty much left the 'fairy tale' side of things, moving more into mythology or fantasy (somewhat DND style), for several of its creatures and areas as well, especially once you reached Mordack's Island. Some of the stuff was inspired by fantasy novels (the snake statues are said to be based on the black Watchers in Return of the King (more so in the way the way they are defeated), and the sphinxes in Fantasia).
In KQ4, you get the scary, human eating troll, with it's talons and glowing red eyes...In
Uh, the troll in the cave has green eyes, and a club... It doesn't have talons, at least none that can be seen.