Kahl is not, in this moment, enraged, aside from passing flares of bitterness, firy comet-tails in the wake of his own stony brittle jealousy. He's not even surprised. Kahl knows what to expect from Hells. He is cold-eyed, if not truly cold-hearted.

Zerxus's anger can have the space and time to emerge, to disentangle from his weariness and pity and defensive pride, precisely because Kahl is not, himself, radiantly angry on his behalf. Kahl is not radiantly angry that Asmodeus has hurt him, or even that Zerxus has continued to let him. He doesn't like it, but he already knows this is what both of them would do; they have not promised him to do anything else. Kahl has not decided in advance which horrors Zerxus ought to be angry about - only that the anger he has deserves the space to burn.

So she was a real threat, Kahl understands, instantly, brutally. She had a real chance, where Zerxus does not, of effecting a change he wished to refuse. And he reacted as he would to a threat.

Interesting.