He currently resides in an alchemy shop named The White Phial, and serves as an apprentice for Nurelion, an old and sick Altmer, whose life obsession is to find the legendary White Phial. Quintus was originally from Cyrodiil, but traveled to Skyrim just for the opportunity to work for Nurelion.
After recovering this Phial during the quest, the Dragonborn discovers it is cracked and is useless in this state. Seeing this, Nurelion gets even sicker and cannot get out of his bed.
After completing the quest "The Throat of the World," Quintus will send the Dragonborn a letter, saying that he can repair the Phial if given some rare ingredients. Reading the letter will trigger the next quest, "Repairing the Phial." Once all the ingredients have been gathered, return to him and watch him repair the Phial. He takes the Phial upstairs to show it to his dying master. As soon as Nurelion finally sees the repaired Vial, he dies. Quintus states that his master died happy, realizing his life's work was completed. However, he cannot stand to have the Phial around anymore, because it would remind him of Nurelion's obsession. Instead, he gives it to the Dragonborn.
After all of this, Quintus will become a candidate for marriage.
"My master can be a bit short-tempered, but I've learned so much from him."
- I have a delivery from Sondas. "Oh dear. Darkwater Crossing needs medicines for its miners? I'll see about getting this order filled right away. Here, a few septims for you."
Nurelion: "I'll be fine."
Quintus: "Master, you're far too old for this sort of journey. We don't know what's inside..."
Nurelion: "I'll...<cough> I can...<cough> just...<cough>"
Quintus: "You see, you're not well! Have a seat and I'll fetch you some tonic."
Nurelion: "Bah, if there was a tonic that could help me, I would have found it by now..."
Nurelion: "Quintus, could you fetch me a copy of The Firmament? I need to compare the old star charts to today's."
Quintus: "Did they really record the star positions from Curalmil's tomb? There's no way it's that precise."
Nurelion: "Confound it, boy, I know what I'm doing. It will help me determine the season of his burial, which I can cross-reference."
Quintus: "I... I apologize, master."
Nurelion: "Don't waste time apologizing, just find the book!"
Quintus: "Master, I have a question about infusions of arrowroot."
Nurelion: "Damn it, child, didn't I tell you to gather my notes on sub-material properties?"
Quintus: "Yes, and I'm working on it, but I'm also trying to..."
Nurelion: "When I ask you for something, I expect it to get done."
Quintus: "Yes, master, I know. I just want to keep up my own projects as well."
Nurelion: "You can waste your own time, not mine. An apprentice obeys his master. A good one does, at least."
Quintus: "Yes, master. I'm sorry, I'll get back to those notes straight away."
Nurelion: "I'm sorry to always be so hard on you, boy. I just worry I don't have much time left."
Quintus: "I know, master. Don't say such things―there is always time."
Nurelion: "Don't be so sure. Now, have you finished grinding the dried snowberries?"
Quintus: "Erm... no. Not yet. I'm sorry, I was reading up on the effects of distillation."
Nurelion: "What? You've been lollygagging in idle reading?"
Quintus: "No... I was trying to..."
Nurelion: "Out of my sight!"
- "My master can be a bit short-tempered, but I've learned so much from him."
- "I'll never have Master Nurelion's skill with potions."
- "Good day, friend. Keeping well?"
- Once Nurelion dies, Quintus will take over The White Phial.