Why should this frighten them? They are fierce warriors, used to wizardry. However, Hugi opines that:
"'...o' late they've seen so much a' 't, and so nasty, that their nerves are close to breaking.'" (p. 131)
Can a place be evil? Not literally, but it can retain an aura of evil deeds committed there - the sites of the Holocaust.
Poul Anderson imagines two extreme examples:
a ruined and abandoned church, its altar defiled by a human sacrifice;
thirteen men around a balefire before a great stone altar with a broken life-size crucifix and a slaughtered baby, creatures waiting in the darkness and a blackness taller than a man forming above the altar...
When a hero conceals his identity even from a potential ally, he generates doubt and distrust:
Holger with the Saracen;
Clark Kent with Lex Luthor.