The Dark Angels are a chapter of Space Marines in the Warhammer 40,000 wargame. Their colors are a dark green base and trim with a white winged sword for their insignia. The source of their gene-seed is Lion El' Johnson. They originally hailed from the planet of Caliban. However, during the chapter's most tumultuous event, the planet was all but destroyed. The only bit of its surface is the now the Dark Angel's bastion, the Tower of Angels. Their flagship is a battle barge as old as the Horus Heresy dubbed The Rock.
The Dark Angels are a stuanchly loyal chapter with the darkest of secrets. During the Horus Heresy, fully half the legion betrayed the Lion. For a summary of those events read Summary of the Fallen Angels fluff.