According to Medieval superstition, Elves were human-size. They could be the cause of sharp shooting pains in our bodies as their arrow pierced us. There are many superstitions about. One of them emanating from the Highlands of Scotland, whereby the first-born should be watched over, lest the baby is replaced by a sickly child or changeling. These superstitions were taken very seriously.
It is Disney who swayed our thinking and portrayed the Elf as small diminutive creatures.
Elves were philanthropic as well as bad. Some of our ancestors thought there were good 'light Elves' and conversely the badder 'dark Elves'. Many stories evolved through folklore and superstition. It is quite easy to imagine centuries ago, no streetlights, living in a village surrounded by trees, the wind howling and the cold cutting deep. Aching bones and sore malnourished muscles could spark these ideas on a dark spooky night.
Elves can die in battle or of a broken heart. So, in this story, it was important that Christine live happily ever after.
Father Christmas, of course would only want nice Elves working for him.
Ideally, Elves are immortal, as was Father Christmas.