One unique trait of these night elves is worth particular note: while most of their people's souls are borne across the veil as expected, certain night elves may also linger in the mortal realm in a soulshape they refer to as a WISP. It is this author's opinion that this phenomenon is caused by the soul's intrinsic bond with the magical nature of its home forest, thus creating a tether that allows the wisp to remain among the living. Though, it should be acknowledged, ,I cannot entirely rule out the interference of Elune, their revered deity, in this matter.
As we well know, beings of her origin cannot, under any circumstances, be trusted.