At that certain era, the blood elf was known as the greatest elven ingenuity.
By the time the young elven children successfully transformed into one, they would already have a level of strength comparable to that of an adult elven warrior.
When they began showcasing their formidable innate ability, most eleven magus can't stop them.
The Elven Queen Azhara was greatly pleased; despite the fact that hundreds of other young elven children were sacrificed in order to allow the birth of a dozen blood elves.
Years later, when they had deemed as ready, one blood elf was all needed to take over one world.
The blood elf then would wage war with the neighboring world, which would result in the total destruction of both worlds. In the end, the said blood elf would be left as the last one standing and successfully advancing its realm. The more war they involve the stronger a blood elf becomes.