“I ask you: are you the arrogant, foolish princess who wants to enslave me in your quest for the Holy Grail — or for endless pleasures and nightmares?”
“Yup! Absolutely!”
A chorus of agonized cries sounded from beneath the ground, and the children’s arms growing around them burst into flames. In the blink of an eye, they were bleached skeletons. Then they crumbled to ash. The ash swirled in the gloom, and the Heroic Spirit loudly declared the contract formed.
“Behold! The pledge is made!"

Fate/Strange Fake: Volume 3, Prologue IX