Time Scout by Robert Asprin & Linda Evans

In a voice faint with terror, Kit cried, “I command thee, in the name of Christ, begone Satan! God will protect us!”

”Satan will eat your entrails for lunch!” Margo screamed right back.

One of the shaking farmers let out a wail of terror, and hurled his torch straight onto the pyre. Wood shavings crackled and roared into flame. Margo screamed, then shrieked at the poor farmer, “St. Nick will have your guts for sausages!”

Kit, not to be outdone, rose tottering to his feet and lifted both arms, trembling so violently even Malcolm was halfway convinced he was about to fall down again. “Jesu Christo! Open the gates of hell itself! Send these minions of damnation to their deaths!”

Then Kit hurled his own torch like a thrown javelin — straight at the source of the sound that wasn’t a sound.

Twenty-five yards down the beach, a crack appeared in the fabric of reality. The torch sailed straight through it. Someone behind Malcolm screamed. Someone else began chanting hail Marys. Another man began to sob. Half the Portuguese broke and ran for town, wailing in terror. The gate dilated open, pulsing savagely in the mad rhythm of an unstable string.

”NOW!” Kit yelled.

Margo flung herself down the pile of burning wood, jumping right through the flames. Kynan Rhys Gower followed with a wild yell. Malcolm caught a blur of motion

The huge blacksmith had aimed his weapon at Margo’s back.

Malcolm lunged forward. He knocked the barrel of the smith’s rifled wheel lock upward just as the piece discharged. The smith roared. Malcolm dodged away. –Then delivered a snap kick that flattened an arquebusier trying to fire on Margo.