Crushing
"To reiterate, the base is the most important, as the functionality of the card is defined from that. Whether the card is elemental, aetheric or has some other nature, it must reflect in the base. Then a card needs an aetheric network which has to connect the spell model with the various layers of the card. The number of layers in a card is represented by the recipe, with the minimum number of layers being three. In that case, the layers are the case, the aetheric network, and the layer that contains the spell model."
The card they were making at the moment, Earths Boon, required five layers, and the fourth layer would be the one that contained the spell model.
Nero had always just directly bought the ingredients which contained spell models, without ever even realising it contained the spell model rather than being just another part of the recipe. This would be his first time.