Elves are the descendants of a hybrid mutation of a pixie and fairy. As it stands, they are rather similar to the dwarf race as both have fairy blood in them. Though the two races naturally do not get along with one another for various reasons. The interactions between the fairies of the long-forgotten past and other races had led to the cultivation of their ancestors.
From the start, the elves were under the protection of a rather powerful illusion type barrier that would distort one's very sense of direction, thus preventing most intruders from approaching their settlement. Since they had lived long lives, their most masterful members had created this barrier to protect them against outside threats. Since their appearances are always extremely attractive, they are also the targets of greedy human slavers. However, their troubles began to occur around three hundred years ago, when the master who had created the barrier had wedded into a foreign nation and left the village. It would seem that a rather heretical and youthful individual of their community wanted to prove their still budding abilities and wished to close the gap between himself and the former master. In the end, he had disrupted the barrier and made living under the barrier's protection rather difficult. This occurred roughly one hundred years ago, just as the war between the Mezu and Gozu had just begun to heat up. Thus, due to the distortion effects causing problems, living within the hidden village had become rather difficult.
They were forced to begin looking into moving their village, though, due to the vastness of the Great Jura Forest, finding a new location to establish their village was proving rather difficult. In the meantime, the number of magic beast attacks had become far more frequent recently, and by this time the maintenance of the barrier had all but ceased. They decided to move their settlement closer to human settlements for security. In the end, this turned out to be the cause of a worst-case scenario as they found themselves attacked by slavers. Monster slaves are prohibited in most human Kingdoms. So while Elves may be one of the species of demi-human considered closest to humankind, they are still treated as if they were monsters. Different from humans, less than humans.
They had attempted a desperate resistance, however, the hunters had extensive experience in such matters. Thus, in the end, the result led to many of their youths being captured. Right after the large-scale surprise attack on their people, they had received word of a Demon Lord's enthronement. Not only that but one who was recognized by the Great Demon Lords at their banquet. They decided that it must have been the will of the heavens for them to hold out for as long as they had, to beg for the protection and aid from the Demon Lord who would come. They had fallen so deep into despair with almost all of their options and hopes exhausted. Thus, in the end, discovering a Demon Lord in the rulership of their forest had become their last hope.
Rimuru accepted their request, granting them aid in rescuing their fellow kinsman.
The elf race is well known for their unusual longevity. As they are said to be the descendents of forest fairies, they have an average lifespan of between five hundred and eight hundred years. There are even those said to have lived even far longer, coming closer to a fairy-like existence.
Their bodies mature into adulthood at the age of 20, similar to the human race, yet stop aging beyond that point. For humans who age constantly until their death, they are a race to envy. Even the elven elders have extremely youthful appearances. They start aging rapidly when they begin to draw towards their deaths, and after roughly twenty or thirty years after the aging process begins, they face the risk of senility, just as elderly humans.
Due to their age, they have a tendency to not readily seek to give birth, nor do they have the most fertile bodies. Due to such reasons, their numbers remain quite small. Because they live so long, their specific village limits the number of offspring that are allowed. This is a rather important aspect of their society.