Where the Evil Dwells

Novel, first published: Del Rey/Ballantine 1982

The setting is a medieval alternate Earth where the Pax Romana has existed for two thousand years but is at last declining. The Roman legions have never succumbed to the barbarian hordes who are kept at bay by the "Evil," creatures dwelling in a buffer zone dangerous to humans called the Empty Land. The Evil are Simak's customary conglomerate of non-humans: unicorns, dragons, ogres, harpies, trolls, ghouls, goblins, banshees, and some nasty elementals - things of evil spawned from dead and decaying matter similar to Theodore Sturgeon's "It."
A company of humans - Harcourt, a young lord grieving for his lost love Eloise captured by the Evil in a terror raid; Guy, the local abbot; and a housemaid Yolanda, who also happens to be a crack archer and expert woodcarver - and a Neanderthal called the Knurly Man, Harcourt's mentor, venture into the Empty Land. Harcourt is seeking Eloise and the abbot has news from Harcourt's dying uncle of a holy relic, a prism in which the soul of a saint has been imprisoned by a sorcerer.
On the way, the questers are joined by Simak's usual odd assortment of characters: a disgraced Roman centurion who fled the scene of a battle, an outcast troll in search of a bridge, a noble lady turned witch to study magic who also turns out to be Yolanda's grandmother, a wizard posing as a peddler, a parrot, and four wooden gargoyles who descend from a cathedral to help the company out of a tight spot.
Despite repeated attacks by the hordes of the Evil, the company fights its way to a Roman villa where the objects of the quest are housed. Ironically, the quest is a failure. Harcourt rejects Eloise who has become a pawn of the Evil, and the prism is dropped and shattered, releasing the spirit of the saint.
Yolanda marries Harcourt and everyone lives more or less happily ever after, except for the Knurly Man who gives his life to accomplish the quest.

Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.124-125