Even if it hadn't actually been a world item, something of comparable level was necessary because of how Shalltear was designed. Being a player from Yggdrasil, Ainz would've referred to it as such out of familiarity if nothing else I suppose.
Wait, was one of those spells seriously a shark-nado?
Pretty much, though given his race and class theme they're probably undead. If Zombie Sharknado isn't part of that movie series yet it probably will be eventually.
@Cleesus they get into it later in the books but it actually was just a random encounter Shalltear had with the mage who mind controlled her. She was in the wrong place at the wrong time.
Props to Shalltear’s VA during this fight in the anime. That crazy laugh she did at the start after Ains attacked her sent chills up my spine and was very arousing ( ͡° ͜ʖ ͡°)