I wonder if it's connected to the 14th and/or Mana. - Exactly my point~! The 14th was a Noah so it makes sense he would have the same spells as the Skulls and he could've taught them to Cross.

Now only to know who's the mysterious person who gave Levellier info on the 14th, the one we glimpsed on that bed... 'Cause, honestly, he's in it too >.> <.