Brother Balthor from the Dark Angels chapter in action...
The Dark Angels have the honour of being the first Legion created by The Emperor. Like the others, Lion El'Jonson was lost while he was still in his infancy. He later turned up on the distant planet of Caliban, which bore some resemblance to early medieval Terra. Luther, who discovered El'Jonson and prevented his death at the hands of his fellow knights, was a member of the Order, an organization of knights, and the two become close friends. The Primarch eventually became the leader of the Order and the whole of Caliban.
Meanwhile, unknown to the people of Caliban, the Emperor was waging his Great Crusade across the galaxy, reuniting humanity and purging entire star systems of their alien oppressors. As the Imperium's wave of conquest advanced across the galaxy, Imperial scouts rediscovered the isolated world of Caliban. It was not long before the Emperor was at last reunited with El'Jonson and was filled with joy as would be a father on finding his lost son. The Emperor's first action was to give Lion El'Jonson control of his 1st Legion. This legion of Space Marines had been created by the Emperor from its Primarch's DNA samples and had fought alongside the other Imperial forces as the Great Crusade was waged across the galaxy.
The 1st Legion was thereafter named as the Dark Angels, in reference to a Caliban legend that told of great, righteous heroes who held back monsters. Announced by the Primarch, the connotation was in fact first drawn by Luther, who quoted a section from the legend upon first seeing Astartes descending using jump-packs: "And the angels of darkness descended upon pinions of fire and light...the great and terrible dark angels."
(source: Lexicanum [link]
for the stock castle,
for the stock flame
Original drawing of the spacemarine owend by GamesWorkshop [link]
Painting done in Photoshop CS.