Skullius' Aura was outlandish, far removed from the norm. When he had first gotten a taste of it, he had noticed that it was rather… strange. It was greedy.
(A/N: Refer to Ch.573).
It had adopted a dark blue hue back then, alerting everyone who had been with him and making Skullius a little hesitant.
When using it normally, it bolstered his strength a little more than that of the overage Advancement Stager, making him stronger when paired with Skullius' already absurd base power, along with the ridiculousness of his skills.
However, all this had been stripped away during the Premium Age Royale. At this point, Skullius would have regarded his death against Rias as the highlight of that entire event. Not only did he meet Irisa in death back then, right after he was revived as result of Gabel turning back time, he used [Swordmaster's Quiescence] on the sensation of death, fresh on his soul, to amplify his already strange Full Body Aura.