Rhin is just a child - nothing special about her. Unless you count her damaged head, her odd turns of phrase, and her tendency to talk to a rock that lives in her pocket. She insists that the stones she carries with her are gods. She says they help her, though it's hard to know for sure. The key issue with Rhin is that she has difficulty remembering things beyond the broadest possible strokes. She knows the gods are a part of the culture she was born into (the town of Baranth), but cannot remember her family or anything else. It torments her to no end.
She suffered greatly upon coming to Sagus Cliffs. Captured by Tol Maguur's slavers, she became a receptacle for the castoff's tides... And the object of her affections. After she escaped her grasp, Rhin hid away in Cliff's Edge, in a ruined building, trying to figure out what to do with her life. That's when the Last Castoff came into play...
Over time, Rhin regains the ability to remember - and remembers that her closest friend, Ahl, actually sequestered her memories away.
Head to Cliff's Edge. The exit to the caravanserai has a collapsed home nearby. You can inspect it to find Rhin huddling in the ruins. A group of three hooded thugs appears, trying to abduct her. Once it comes out that they're bounty hunters on her trail, she will claim that you have Discoverer's Rights to avoid being taken back to the slaver in Circus Minor. You have three options to deal with them (one, admitting that you're there for Rhin is... Bad). The other three are Intellect-based (Intimidation, Persuasion, or Deception). This will earn you Rhin's loyalty and companionship.
Companion
Rhin is defined by the conflict in her mind. Talking to her requires patience and working over the issues she has. Your interactions with her take a major step forward when you reach Miel Avest and talk to Aadiriis. She asks you about the Tides and then you can inquire about what Tol did to you, then promise her (or not) that you won't use the Tides in the same way.
Her next major storyline step is after you escape Miel Avest and reach the Bloom. She will take to Ahl and realize that her Memories were actually hidden by her closest friend, the god of hiding, and suffer a crisis of faith.
Finally, you come across Aen-tozon in Little Nihliesh, allowing you to send her home. After the first feeding, talk to Rhin, then to Aen again. He will mention that he needs a different kind of sustenance: Wondor. Talk to him, then to Aen-tozon again. The portal will open and you can ask her to go home... She will thank you and give you the God of Finding, then disappear. Make sure to strip her of all cyphers and other gear first!
Notably, you can dump Rhin early in the game by talking to Alcen Perie about the House of Empty Time and convincing Rhin to leave for a better potential future.
Intellect-based (Intimidation, Persuasion, or Deception). This will earn you Rhin's loyalty and companionship.
