More thoughts:
The Angelos are perhaps a very ancient bipedal winged beings, very lawful and having a preference for a very ordered universe. Much larger than most other humanoid species, their vessels are correspondingly that much larger than their counterparts of other races. Angelos technology is vastly superior to just about all Alpha Quadrant species and perhaps many others, including the Borg and 8472.
Their nemesis, the Hellions, represent chaos and death. Enemies for millennia, their war has raged on for just as long, spreading ever outward as both sides fight for mutual extinction.