The Dark Elves come from Svartalfheim, led by Malekith. They mainly are the foes of Asgard. Recently, the Bifrost has been broken and without that bridge, Asgard can't keep control over what's happening in the rest of the Nine Realms. The Dark Elves are taking advantage of this. They've found a way to create portals out of Svartalfheim to London.
Leader:
Malekith
Members:
Kurse
Typical Dark Elf Duskguard
Typical Dark Elf Cannoneer