Kain's breathing became even heavier, but after experiencing so much exhaustion, Kain had gradually gotten used to this feeling of mental fatigue.
Using a mid-class magic skill twice in a row wasn't easy to handle, and Kain had already expended a huge amount of energy killing a bunch of Crawlers before.
However, Kain still could not rest, his intuition told him that tonight would not be able to pass peacefully like that.
And it seems his intuition was right.
As Kain delivered the finishing blow to Nightcrawler, swarms of Crawlers rushed out from all directions in front of him. The timing was so perfect that Kain assumed the Crawlers had been waiting for this moment, because before that, Kain had not seen any Crawlers advance, or even appear at all.
They only appear when they see him weakened.
"Although they have not yet awakened true wisdom, these things... have formed some primitive cunning thinking."