FromSoftware's revered Dark Souls trilogy brought the gaming scene a rich, compelling dark-fantasy universe and engaging action RPGs. This sprawling world spawned a wide variety of characters--if mysterious ones. Dark Souls III introduced the player to discover new characters--and iterations of older ones--that uncovered new pieces or lore while tying to lore from previous Souls games, each with something interesting to offer from gameplay, narrative/worldbuilding perspectives.
Many of these characters were an integral part of ending on a high note and keeping players engrossed in the world in-between and during their grueling adventure through this equally mysterious world, and FromSoft's unique brand of subtle narrative approach.
Cornyx Of The Great Swamp
This Firelink Shrine's pyromancy teacher is Cornyx of the Great Swamp, and on top of the bits of lore and worldbuilding he provides, he's also a great character simply for being a humble beacon of brightness. The Great Swamp is referenced throughout the Dark Souls franchise as part of pyromancy's origins. Most practitioners come from there, as pyromancy requires closeness to nature, which the Great Swamp offers plenty of.
Cornyx is refreshing to talk to given his aforementioned humility and enthusiasm for knowledge, and equal amounts of enthusiasm for teaching and learning with the Ashen One as his pupil. A great teacher knows there's always more to learn, and from a variety of perspectives.
Yuria Of Londor
Londor is, essentially, the land where the Gods kept their undesirables from revolting against Lord Gwyn's reign, and Yuria of Londor appears in Dark Souls III to play a key role in the shaping of the Ashen One's story. Namely, she's key to the Usurpation of Fire ending where the Ashen One decides to usher in the Age of Dark that Gwyn and his allies fought so hard to avoid.
In-game, Yuria replaces Yoel in letting the player unlock extra Soul Levels at the cost of Hollowing, giving an extra edge. She's also one of the three sisters (including Friede) who founded the Sable Church to serve Darkstalker Kaathe; the primordial serpent that encouraged the Chosen Undead in the first game to usher in the Dark.
Painter Of Ariandel
Sister Friede betrayed the Church to attempt to link the First Flame, but failed, became Unkindled Ash, and entered the Painted World of Ariandel. She guards the Painter against seeing the Flame, prolonging the rotting world. The Painter is unaware of Friede's political manipulations, preventing the Ariandel's Rot from being burned away so that a new, cold--but gentle--world can be painted.
The Painted Worlds were originally created by the Gods to further restrain the parts of humanity that threatened them, creating thematic parallels. Though the Painter is a soft-spoken, mysterious character, she offers a lot of intriguing lore questions, and her ties to Gael's mission make her even more fascinating.
Unbreakable Patches
It's somewhat strange to suggest Patches--a recurring character infamous in FromSoftware games for making players' lives difficult--a great character, but it's partly from that loving gimmick that he is. Unbreakable Patches picks up from where he left off, first meeting you by trying to throw you to giants in the Cathedral of the Deep.
His questline gets interesting, and surprising for his usual character, as he begins to show some of his humanity and compassion for Greirat. Once the thief gets more reckless in getting treasures for the player, Patches progressively gets more and more concerned for his safety, and even rescues him if the Ashen One plays out the questline a certain way.
Horace The Hushed
As the name suggests, Horace the Hushed isn't much of a talker but manages to make for a good character by association. Along with Anri of Astora, Horace was the only other child to survive the ravenous appetite of Aldrich, Devourer of Gods, and Lord of Cinder. The way Anri talks about their friendship is heartwarming and inspiring to see in Dark Souls.
His backstory makes things more compelling, as it's suggested he may be a Blue Sentinel who survived a dangerous encounter of the cultists of Rosaria's Fingers; a covenant that offers severed tongues to their speechless god to be "reborn" in exchange. Like with other tragic characters, seeing them separated only for the Ashen One to discover Horace presumably Hollowed in the Smouldering Lake, forced to kill him, devastating.
Slave Knight Gael
The Ringed City completes the part of the Dark Souls III story--and the series in general--that started in the Painted World of Ariandel. With it, is the aforementioned Slave Knight Gael, who was a parental figure to the Painter. When the Ashen One first encounters Gael, he's pleading divine intervention and chanting for "fire to Ariandel."
The Slave Knight was just what his title says before serving the Painter, and he ventures to the Ringed City in desperation to find "the Dark Soul of Man" so that he can bring it to her to paint a new, revitalized world free from the cyclical curse that Gwyn placed. Unfortunately, he finds his intended pigment dried, with the Ashen One meeting him to battle--and as one of the most powerful bosses in Dark Souls. In tragic, but necessary irony, it was Gael's blood that the Ashen One needed to use as a pigment for this new world.
Ludleth Of Courland
Ludleth of Courland offers important gameplay mechanics for the player's treacherous quest, giving the option to churn Lord Souls into valuable weapons and other items. It's a crucial feature to acquire gear like Havel's Ring and the Wolf Knight's Greatsword--both great for Strength builds in DS3. Though, he's among the best characters at Firelink Shrine for dives into lore.
Even his gameplay function, transposition, is good worldbuilding, as it's an art demonized like pyromancy that got him exiled. He himself is a Lord of Cinder and can be heard having night terrors of the pain brought presumably from linking the Flame.
Greirat Of The Undead Settlement
A character that would normally seem inconsequential to such a vast fantasy world--and was seen as such in his life--is Greirat, but he proves to be among the most wholesome characters in the game. Once a resident of the Undead Settlement below Lothric, he seemed to have become a sort of Robin Hood, but it eventually caught up to him as he was imprisoned in the crumbling kingdom.
Upon being freed, he helps the player in return for giving a ring to someone clearly he loves named Loretta. Once discovering her death and after grieving, he seems reinvigorated in thieving for the Ashen One for a new purpose--and seemingly out of friendship, making his questline all the more emotional and investing for the player.
Anri Of Astora
Anri's gender will be the opposite of what the player makes their character, but the origins will be the same. Aldrich established themselves as the Devourer of Gods to bring an entirely different age: the Age of the Deep Sea. They ate sacrifices to grow, but when Anri and Horace escaped, they forged that bond and made it their life's mission to slay the Lord of Cinder, keeping from spreading his horrors further.
Anri is a joy to meet on the Ashen One's quest, as they have a genuine sense of human compassion and empathy. Theirs is a questline that's more worth seeing out to the end, as Anri is a rare friend in this bleak world.
Siegward Of Catarina
When it comes to rare beacons of hope in the Dark Souls universe, Siegward of Catarina undoubtedly takes the cake. He's a fan favorite and a spiritual successor to Siegmeyer and his daughter Sieglinde, and almost incites the same level of relief when meeting him as with discovering Bonfires.
His indomitable spirit in the face of the many adversities this cruel world throws everyone's way is inspiring, and Siegward's probably the best friend the Ashen One could ask for here. His questline of returning to help bring his friend Yhorm the Giant to rest is among the most emotional, bittersweet plot points in the series and will always be fondly remembered.