Talked to the revisions team,
this image implies something more akin to a 1-A powernull that actually killing SK, as it is described as being a "more powerful magic than himself", and killing him by duplicating him and suffocating him, which is more akin to powernull in it's own right. Also it is not 1-A durability either, because powernull. This also fits with it's invulnerability to most things that don't include consuming it directly.