I suppose we're meant to build on what's been posted? Ok, I'll give you your Elves. This represents my attempt to blend Tolkien-esque Elves who are tragic, benevolent allies of men against the forces of evil, with older, fairy-tale Elves who are mercurial jerks of uncertain morality.
In the Fair Folk, the realms of men find but uncertain allies against the Necromancer. Though certainly they have no love for the Necromancer's dark designs, neither do they feel kinship with the folk of the towns, or with the knights in their keeps. Their Law is old and wild, its rules labyrinthine and its penalties severe; and men have, oft and oft unknowingly, built up a great many score of transgressions 'gainst the Fair Folk; and they in turn remember the reprisals for these transgressions: their crops withered by the Fair Queen's frosts for bridging a stream, their villages raided by the Fair King's riders for planting oaks alongside birches. The country people are wise where knights and burghers are foolish, and have learned, if not the Law itself, how to avoid breakig it, and how to propitiate the Fair Folk where it has been broken.
But it is not these ancient feuds alone which keep the Fair Folk occupied. Their realms are ruled by the Dance, a cycle as old as the earth, in which the King and Queen make love and war with one another in shifting seasons. Few elves give themselves wholesale to the King or to the Queen, but all feel the stirring of the Dance in their hearts, the desire to be swept up and submerged in it. They know, by painful example, that to follow the Dance leads to sorrow and death. The life of an Elf is measured not in definite span of years, but in how long his individuality can assert itself against the rhythm of the Dance, before he joins it to his doom. It is for this reason, to forestall the grip that the Dance tightens over their souls, that many Elves voyage to mortal realms, and interest themselves in the affairs of men; but it is only ever a delay before the Dance calls them home and claims them in its sweep.