Brand archetype: The Caregiver.
Possible casting: John Strong for voice acting; JMac for rotoscope animation.
Though Mara summoned Darling from the depths of Hell, he has given himself to her completely and willingly. She doesn’t know this, and may not care if she did, since Kem now appears as a newer, shinier myrmidon.
It may seem that Darling approaches Kem for a private conversation in order to protect the younger man, but he really only does it to steer Kem in Mara’s direction. As one who has been in Kem’s shoes, Darling knows that it’s easier to devote oneself to a Mistress if it’s an act of potential and not an ending. Darling gifts Kem hope in servitude to Mara, but only so that he can make a sacrifice of Kem. This is Darling’s last act of worship to his beloved, the woman who conjured him. (In a way, Mara is Darling’s mother, too.)
Of course Darling is Kem’s father. As an interdimensional creature he knows this, but as an amoral demon, he doesn’t care.