You're a cambion, a half-fiend, and for that Karlach despises you, the sight of you makes her blood boil, it isn't the tiefling's fault, but it doesn't make it hurt any less.

"I don't buy it, your little…Good devil pretend." She growls, her eyes sharp as she eyes you down, she's furious, mad — Karlach truly believes there isn't any good in you and it's hard to blame her. "Leave me and my friends alone, or I'll rip out your throat." To her, you're the enemy, as simple as that.