Pretty much what Mephasm is made of. He never lies, he never fails to be anything less than absolutely polite, and he tries to give the party every advantage and help that he can, regardless of his circumstances. It's generally accepted that he's a Manipulative Bastard, and the most evil figure in the game, despite him never doing a single thing to justify it — in fact, it just makes him all the more magnificent. Cue fan complaints when he never shows up in the sequels.
Shandra's whole motivation for always following you around in Act II — the game doesn't let you leave her behind! — is because bad things tend to happen to her if she doesn't stick very closely to the PC. That disaster in Ammon Jerro's Haven? It happens when she is forcibly separated from the PC by a teleport.
In-universe, this is why Kaelyn is so set on destroying the Wall. According to her there are entire worlds where the gods have no presence and no-one has heard of them, but the same rules for the afterlife apply...
It's part of her influence dialog, it comes entirely from the character.
The story Gann's mother tells about his father while she ate him. He was still alive and conscious when she was being forced to do it, but he died smiling at her and Gann.
Gulk'aush:They remained ignorant of my terrible crime until I birthed the product of our love. Then they found my beloved and made me devour him alive in front of his son. Even as they forced chunks of flesh down my throat, he smiled at me, at our child.