With the plethora of spells in his arsenal, Blake had a lot of options he could choose from. And if his goal was to simply defeat the humanoid demon without any strings attached, then a single spell instantly came to his mind.
One that had never really failed him before. There was a moment where the spell failed to do its job to kill Blake's target in one hit, but it was due to his own incapabilities, overestimating his nether capacity and almost falling unconscious at the last second before the spell was aimed properly.
But other than that, Blake trusted this spell as much as he trusted himself to do its job. Different from back then when he had exhausted his nether, the current Blake had a significantly larger nether capacity and he had not been spending his nether a lot before he started fighting the humanoid demon.