At last the giants and trolls were mastered by human tickery.

A cleric persuaded a mountain dwelling troll to do the work of building a church.

The price the priest offered was the sun.

The priest could not possibly pay such a price and never meant to. While
the creature was working on the church the priest wondered around the mountains in search of the trolls name.  This was the weapon the priest
needed :  Trolls were an ancient race, their names were full of magic and not to be given into human keeping, for the mortal who knew a troll's name gained power over the old one.

The priest came upon a cave were another troll was making food.  She
shouted at the children that their father would be home as soon as he finished the church...

The priest waited until the church was finished.  Then he stood below the structure and called out, " Tvester! ".  The troll gave a horrible cry and fell
to the ground, dying before he struck it....