The Fomorians from Irish mythology are steeped in mystery. It is unknown where they came from, or the length of time they had knowledge of Ireland, and what actually happened to them. Lady Gregory describes one Fomorian habitat as a glass tower in the sea. Many people describe them as sea fairies or sea monsters. My best guess is that they were Nephilim!
Sea monster accounts are found in virtually all cultures that have contact with the sea. For example, Avienus relates of Carthaginian explorer Himilco's voyage "...there monsters of the deep, and beasts swim amid the slow and sluggishly crawling ships." (lines 117-29 of Ora Maritima).
Windjammer: #Windjammer ~ Cthulhu is a monstrous entity who lies "dead but dreaming" in the city of R'lyeh, a place of non-Euclidean madness presently (and mercifully) sunken below the depths of the Pacific Ocean.