Cut off

Nial was still a little baffled about the voices in his head but he didn't hesitate to kill the Originals around him. Spikes manifested of darkness pierced out of the ground and dug deep inside the body of the Originals, whose voices resounded in his head over and over again.

Their gratefulness could be sensed clearly, and, even more so, the suffering and pain they had gone through for countless years before he freed them of it.

Nial chose to ignore gratefulness because he would have annihilated the ancient civilization whether the members of the ancient civilization would be grateful or not. Their emotions didn't impact the course of events in the slightest.