Skullius had been slowly mastering [Evil Darkness], beginning with a method to avoid wasting darkness as he usually did when trying to maximise the stat benefits he was granted!
The way he found most effective while keeping the massive boost effect was to shape the darkness into a fixed shape that didn't leak any excess.
It had taken some time for him to find out which shape was most suitable, but after looking at the space he spent his time in, the cell, he finally made a decision.
A cube would be best.
He practised by trying to fill the entire cell with the darkness and maintaining the shape as the darkness conformed to the structure of the cell.
With the continuous practise and the use of [Advanced Evil Weaving], Skullius finally forged, the skill, [Perfect Night Domain].
Frankly, this wasn't a name he chose but one that was recommended by Oliviana when he asked a hypothetical question that used the traits of the domain as content.