The Sidhe in Bryn Mawr, or where did the elves go

As an experiment Im going to try and list some of the material Ive pondered up already in little bites that I can go back and expand later.

So first up are the Sidhe, the elves of my world.

• the Sidhe are mysterious and insanely powerful
• common folk leave them offerings to appease them
• immortal except for violence
• cant lie, but they have thousands of years experience manipulating the truth
• non Sidhe life is viewed like animals
• very much like nature spirits, linked to the land and showing the condition of the land
• spend most of their time living in their own lands/little world
• occasionally they steal children, leaving changelings in their place