Hekatonkhire's aren't 'what remains of a deva after it's dead' the way ghosts are 'what remains of a mortal after it's dead.' They are 'what's remembered of a being of great power by the Underworld,' and even that definition isn't all inclusive. Really, the best definition for the term is 'powerful thing running on Underworld essence that does not fit any other category.' And I'll repeat; there are powerful things running on Underworld essence that are not representative of anything that ever walked on Creation before.
An Event? Sure. But even such a grand event isn't going to do much; demons they may be but their very Essence is torn asunder and scattered to the 5 corners of Creation and beyond when they are killed, with nothing left to tie them to anything. It might cause a shadowland to form at the site of its death, it might not, but as it's not tied to the reincarnation cycle I would bank on it doing absolutely nothing at all, no matter how clamorous its death cry is.
Now, the mortals it might kill in the event, that's something different, and they might remember enough of it even in death that the Underworld is marked by their memories and gives rise to a new Hekatonkhire birthed from the horrors they remember of the fight...
The Underworld? How would it remember? Erembour's Essence would be scattered, quickly diluted, processed and remade within the vast network of power that are Creation's ley lines. Unless she died somewhere close to, or within, a Shadowland it's unlikely that any of it would reach the Underworld in the first place.
Now, the Yozi would know, and feel the worst of it, but that's because the bulk of her existence is there, within the great prison that is Malfeas. That little, barely worth mentioning thimble of power and awareness that was Erembour's incarnation in Creation, that's nothing that can't be handled.
