" What are you thinking of? Dairine demanded. Let me help you—
You need to stay here and let me do this, Roshaun said.
But if I can just—
You can’t, Roshaun said, looking at her with that infuriating, amused expression. But then that’s what “Guarantor” means. If the world can’t pay the price…if the people around you can’t pay the price…you do.
The price? No! Dairine said. No! You don’t even like my little planet—you said so—
No, Roshaun said. Which is possibly the best of all possible reasons to do this.
He stepped out of the wizardry.
“No,” Dairine whispered. “No! Roshaun!”
Roshaun vanished into the fire. "

― Diane Duane , Wizard's Holiday (Young Wizards, #7)