[HoneyBadger]

I think Ungoliant would fit better as a Pretender-chassis than a national summons, just because we're talking about a dark spirit (and one even the mighty Vanir were afraid of) who took the form of the first spider (albeit a size 6 spider) and co-conspired with Melkor on pretty equal terms. Melkor, the mightiest and by far the evilest of the Vanir actually needed to be rescued from her by Balrogs (note the plural) when he refused to give her the Silmarils. It just would, in my opinion, be more interesting to use her as a unique and powerful, but chaotic and difficult, asset to a nation, where you could express her abilities more fully rather than tone the concept down drastically for the purposes of balance. Even with demonlords you know there are three of them. Admittedly, she's one of my favorite characters from the Silmarillion for putting the kybosh on the Vanir's plans for elven heaven and just being seriously scary. Mythological elves are interesting, fantasy elves taste like chicken. Eternal enemy of the Sun sounds REALLY fun!