Population Migration / Travel
Where the elves first descended from the Feywild into the material plane to settle into the trees, getting the aburpt realisation that they aren't alone in this plane.
The elves were in a small number, only 500 or so. They built their own colonies and lived in them for 25 years, hunting small game and practicing their own magic. The first race they encountered were the dwarves, and their battle was evenly matched between intense crafting and weaponry and immense spellcasting talent. The conflict was resolved by Lady Ashilda of the dwarves and Lord Velonrar of the elves, and the dwarves have had a mixed relationship with the elves ever since