Lucifer is a 6'5" strongly built fallen angel with long black straight hair. Wielding his greatsword, he led a rebellion of exactly 200 other angels (much less than a third of the host of heaven).
In the fighting, he personally killed and wounded several angels, Azeigial and Alexial among those killed. One of his two younger "brothers" -- some angels are created in sets somewhat like brothers -- Mikhail (aka St. Michael), in a rage over the killing of his friend Alexial, pierced with his own greatsword the lung of Lucifer, grievously wounding and defeating him.
Lucifer was dragged by Mikhail to Gods throneroom, where God, after hearing the testimony, banished Lucifer and his followers to hell, a realm which already existed, populated by races of (non-fallen-angel) demons. These pre-existent demons became subjects of Lucifer, as God allowed him to rule that realm. God employed Lucifer as a foil to strengthen mankind, giving him some license to tempt people.
Before the failed rebellion, Lucifer, having been originally created a four-winged Cherub, had been granted the high honorary title of archangel, and he was in line to be promoted to a six-winged Seraph (there were only six Seraphem at that time). Believe it or not, he may yet be allowed by God back into heaven, after being forgiven....
Lucifer is a fallen angel.