Kell has to remind himself why he decided to attend the execution in the first place. He wanted the woman dead. He wanted for her to pay for what she did. To him, to other Summoned, but most of it, to all those helpless natives that nobody cared about. He did not expect the punishment would be so gruesome.
It's not just creepy, it's revolting. He visible flinches at each sound of bone breaking. It's nothing his own magic is not capable of - even if forbidden - but the sheep sacrifice and ritualistic nature of the whole affair skirts too close to what her and her minions where doing in the cave. The realization of those similarities makes Kell feel all the more uncomfortable. He regrets coming even before the birds appear.
But the birds do not disturb him as much as the silhouette of the ... entity? being? that calls them. It's one thing to deny the existence of the gods when they're only invoked by their believers. Kell can hardly question what he sees with his own eyes.

In his disgust and discomfort, Kell must have gravitated towards the first familiar person he recognizes in the crowd. He doesn't notice Jesper until the man speaks. The difference between them couldn't have been more jarring.

"I wouldn't exactly call that entertaining."