Andre is a relatively short man, sporting long white hair that is tied back into a long ponytail, and a long white beard. Andre appears to have a multitude of tattoos and wears pants, a belt, and gloves. While similar in appearance to the Andre of Astora from Lordran, they are not the same person.
Andre allows the player to upgrade and infuse weapons, as well as reinforce their Estus Flask to increase its number of uses. In order for Andre to upgrade the Estus Flask, the player must bring him an Estus Shard.
Andre allows the player character to allocate between a standard Estus Flask and the Ashen Estus Flask. For example, if the player has five Estus Flask uses in total, they can choose to have three standard Estus Flasks uses, which recover HP, and two Ashen Estus Flask uses, which recover FP.
Andre can infuse weapons if the player brings him various coals found throughout the world. Certain coals yield different infusion upgrade paths. Once a weapon is infused, it may still be upgraded by using the type of titanite specific for it. However, the player should take into consideration if infusing a weapon affects it negatively, according to their stats, or if doing so will remove its scaling bonuses.
In addition to upgrading weapons, Andre can repair those that are totally broken. He cannot repair the Ring of Sacrifice, though.
The following coals provide the corresponding imbuements, as long as the player has the matching gems:
"Well, a newcomer I see. I am Andre, I serve in this shrine as a humble smith forging new weapons. You're in search of the Lords of Cinder, I trust? A toilsome journey, I wager. You'll require good arms. Let me smith y' weapons. I am a smith, such is my purpose."
"Prithee, be careful. I don't want to see m' work squandered!"
"Weapons and protection are sturdy enough, by and large. But when overused, they'll eventually break. When their durability is low, repair becomes a necessity. Use a powder, or simply rest at a bonfire. But should chance impel them break, bring them to me. I'll hammer 'em back into shape. They take no pleasure in breaking, I assure y'. So handle them with care, if y' would."
"There are two ways to smith weapons. Simple reinforcement is one, and infusion the other. Reinforcement is straightforward. It strengthens a weapon without altering its property. Infusion is a more advanced form of smithing that infuses an element. Reinforcement requires titanite, and infusion requires gems. Bring the stones and I'll do the smithing. It's m' purpose, afterall! In battle, y' weapons are yer only friends. Forge them well, and they won't let y' down."
"Oh, by the by. If you find any Estus Shards, bring 'em 'ere. They can be used to reinforce either of y' Estus Flasks. Without those flasks, you'd want for life or focus. And they'll always stay with y', why not treat 'em well?"
"Ahh, another matter. Infusing weapons with gems requires a special kind of coal. My humble coals won't be any use infusing more unusual gems. I know, it's an awful shame, but it's all I have. Oh, please, don't give me that look. Believe it or not, I'm quite thin-skinned."
Giving him the Farron Coal
"Oh, my... this coal is from the Undead Legion... Used to forge the weapons of Farron's Abyss Watchers. A fine prize. I'm honoured to be endured with it. Now I'll be equipped to infuse special gems. Praise the gods, eh. Time to put this brawn to use!"
Giving him the Sage's Coal
"Well, well... What's the Undead Legion doing with a coal such as this? I'd heard one of the Crystal Sages had sided with Farron's Abyss Watchers. I suppose it must be true. You should know, this coal is imbued with magic. First one I've ever seen. Hardly a surprise is it? I've never been one for books or wise men."
Giving him the Profaned Coal
"Lords... Where didye hap'n upon this coal? This is much too dark. I see the Abyss in it... Yet, a smith I remain. I won't turn down a request. But forget not, Your fight is for the flame, and for y' fellow kin. Just like mine. A cursed fate this may be, but hope remains, does it not?"
Giving him the Giant's Coal
"My, my. the coal of that peaceful giant... Seems like ages past... I imagine his passing was long ago. I miss the old bugger, I do. My thanks. I'll be sure this coal is put to good use. I'll be smithing weapons never afore seen by the likes of y'. It's but a small service, to pay my humble respects"
Twinkling Dragon Torso Stone, once Hawkwood leaves Firelink Shrine
"Oh, you've returned. I was hoping to see y'. That crestfallen arse Hawkwood, he handed me this. He's changed a great deal since he left this place. Graven of face, he asked me to give it y'. Well, now that that task is concluded... What would y' ha' me smith today?"
When attacking him
"Enough of that!"
"Beshrew your heart..."
Talking to him after killing him
"Overstep not your bounds, cousin. I may serve, but I'm no slave. I have business I must attend, begone."
↑http://soulslore.wikidot.com/das3-interviews (March 2016 Famitsu interview with Miyazaki): the interviewer asks "Is the appearance of Andre, the blacksmith, a result from finishing a chapter of the history?" To which Miyazaki responds: "Um. Rather, Andre is there for a minor amusement. Actually, since the first Dark Souls, we were developing him as a part of 'the Clan of Andre, the blacksmith'. And we thought all those Andre looking corpses with embers were exact look-a-likes, and this time, it is the same idea. [...]"