Madesi is one of the few remaining traditional Saxhleel jewelers within Tamriel. Bandits and other such troubles have made journeys to mines and other towns difficult. His profession becomes more and more difficult each day, thus he asks the Dragonborn for assistance with obtaining supplies. He rewards the Dragonborn with gold and an item of jewelry.
1+ Flawless Sapphire can be received as reward from "Dravin's Bow" obtained from Dravin Llanith in Merryfair Farm. The gemstone set is random, but saving before returning the bow nets players different gemstone sets every time. A character below level 20 cannot get 2 Flawless Sapphires as a reward from this quest.
1+ Flawless Sapphire may be obtained from a locked Chest located in the Lockpick Practice Room off of Cistern area of the Ragged Flagon. One chest will have a flawless gem, but not always a Flawless Sapphire.
1+ Flawless Sapphire may be obtained from a Chest located in Ruined Mining Camp at Alftand. This is level based. Locations which have a chance for these gems to appear are not fixed and what one player finds is no guarantee another player will find the same item.
1+ Flawless Sapphire may be obtained by mining for Ore; although, a somewhat rare occurrence.
1+ Flawless Sapphire may be obtained from dead enemies as drop items, but are very rare.
1+ Flawless Sapphire may be obtained from a Dwarven chest in the Jarl of Markarth's throne room, occurrence is random.
1+ Flawless Sapphire possibly received if you help the Jarl of Riften's son, by fetching his blade from the nearby blacksmith he'll give you a flawless gem (or gems) and some gold.
1+ Flawless Sapphire may be obtained from a Dwarven chest in Raldbthar, after killing Alain Dufont.
Quest markers do not appear on the map for Ringmaker errands. (This is because they do not have specific locations. mammoths, NPC's, randomly spawned in chest, etc.).
If the Dragonborn is Argonian, upon exiting conversation with him, he calls them "Marsh-friend". If the Dragonborn is not Argonian, he calls them "Land-strider"
Madesi (and other vendors in Riften marketplace) can be killed by Thieves guild members in the random fights.
Despite being a jeweler and wearing expensive clothes, he sleeps in Beggar's Row on the lower platforms of Riften at night, most likely because of the troubles in his work.
A conversation about this can be heard in Haelga's Bunkhouse, where Svana Far-Shield asks him to take up residence in the Bunkhouse. Madesi replies that he likes the cold and dampness of Beggar's Row, though Svana thinks it's because of discrimination/troubles at work that keep him there.
He can be killed by a dragon (or any other enemy/character) making it impossible to finish the ringmaker quests. (Save can be reloaded of course).