User blog comment:Pualover/Overlord Power Level/@comment-138.162.0.42-20150910182203/@comment-25356962-20150913101136

Ainz know the castle maybe because it's in his area (in vol 1 ainz ask if there is any flying castle like or not), it shouldn't be a very powerful guild, but since ainz isolated himself to other player, the chance he know the member of its guild can be low. For WCI, i think it's RNG with super low chance to obtain them, but at least located in high level place. And isn't ouroboros in nazarick possessing? Or i'm the one who read it wrong