Ilios and Imisela are the Light Incarnates, the sentient incarnations of the energies produced by natural phenomena, as are all Essence Incarnations. These two siblings represent day and night respectively.

Not wanting to be left in the dark, Imisela, the Night Incarnate, picked up a habit of... suffice to say, playing around with mortals in the convenient darkness of her nights. Such practice is generally frowned upon among the Incarnations, though her brother, Ilios, the Day Incarnate, is quite jealous of her for all the attention the mortal populace gives her, as opposed to himself.

Despite that, however, the two have a close sibling relationship between them.
At times, maybe, a bit too close.