Final answer:
Merlin makes King Uther promise to give the child they create to him.
Step-by-step explanation:
Merlin makes King Uther promise to give the child that they create to Merlin in exchange for the opportunity to have a night alone with Igrayne. This child is later revealed to be Arthur, who becomes the legendary King Arthur of Britain. This promise is significant as it sets in motion the events that lead to Arthur's birth and his eventual rise to power.
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