Skraal was alone, eating some meat and bread with a good beer. He was thinking of further battles, and he is expecting some big shots to come.
As a necromancer in the core. His battle stance and battle type involve most of the time conjuring necromancy creatures in front and using them or controlling them to fight.
This is what is expected by the magi.
Most of the time, people would not expect a necromancer to use the different and usual spells of other people to have enmity towards other beings. At least it was not the usual thing that could be expected from a necromancer.
Skraal knows this too and uses it to his full advantage. But he was lucky, as he did not encounter a being at his level and had the same position to fight against himself.
Not counting the Ghost Tower. It was like that in reality. There are not many beings who have created and have some sort of idea that they are capable of destroying themselves.