This writeup is about a fictional character from the game Warhammer 40K. Unless you're already acquainted with the game, this information will make very little sense. So if you're interested, read up on wargame, Warhammer 40K and Blood Angels.
Sanguinius was the Primach of the Blood Angels Space Marine Chapter. Like the other Primarchs, he was cast into the Warp by evil powers in his infancy. Because of the protections placed upon him by the Emperor, Sanguinius' incubation pod survived long enough to carry him to an inhabited world. By the time he arrived there, the corrupting forces of the Warp had caused Sanguinius to mutate and sprout white, feathery wings.
Sanguinius touched down on Baal Secundus, the second moon of the planet, while he was still an infant. Baal and its two moons had originally been fabulously suitable for human habitation, and indeed, thriving colonies existed. But viral and nuclear warfare had reduced the system to wasteland status, and the surviving humans to primitive scavenging tribes, constantly at war with each other.
Sanguinius was discovered by a tribe called Folk of the Pure Blood (The Blood for short). On noticing his tiny wings, many of the tribe wanted to kill him. You can imagine that on a radioactive world, mutations would be both feared and abhorred. However, in the end, the human vulnerability for cute babies obviously won through, because they let Sanguinius live and become part of the tribe.
Sanguinius' growth is notably phenomenal, even among the Primarchs. At three weeks of age, he was the size of a three year old child, and rumour has it that he killed a giant fire scorpion with his bare hands. We don't know exactly how big or dangerous a giant fire scorpion is, but I'm pretty confident it's not the sort of thing your average three-week-old (or three-year-old for that matter) can handle. After one year of growth, he had reached adulthood and the height of his powers. By this stage his wings had fully matured, and he could actually fly with them. As if opening a can of whoop-ass on giant fire scorpions wasn't impressive enough, when a band of more than a hundred mutants attacked the tribe, Sanguinius killed them all single-handed.
The Blood adopted him as their leader, and he led the tribe to greatness. Sanguinius (the "Blood Angel") was worshipped like a god.
That's when the Emperor, using his amazing psychic powers, tracked Sanguinius down and was reunited with him. Using Sanguinius' gene-seed, 10,000 warriors were formed into the Blood Angels Legion, which promptly joined the Emperor's crusade.
At the time of the Horus Heresy (see Warmaster Horus), Sanguinius and his Blood Angels remained true to the Emperor, and were a major part of Earth's defense. At one stage, Sanguinius engaged Horus in single combat. Although he was defeated and slain, he was able to open the chink in Horus' armour which allowed to Emperor to prevail, and kill the traitor.
This information has been gleaned from the book "Codex: Angels of Death" written for Warhammer 40K Second Edition.