You will meet Thiollier as you progress the main story of Elden Ring: Shadow of the Erdtree, and completing his sidequest can bring some valuable rewards. The master of poison is a powerful ally and an interesting NPC who you will encounter a few times as you play. Each time you see him, you will learn something new about your fellow Tarnished on your journey towards finding Kindly Miquella.
Your first few interactions with Thiollier are those of a merchant. After finding him for the first time, he unlocks as a vendor where you can purchase grease, darts, and other crafting items alongside the 
Deadly Poison Perfume Bottle. This weapon does poison damage, so it’s useful when you want to damage enemies over time. Here’s everything you need to know to fully complete Thiollier’s quesline and gain him as an ally.
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Where To Find Thiollier In Shadow of the Erdtree
Thiollier’s Exact Location
Thiollier can be found on the east side of Gravesite Plain for the first time in Elden Ring. From the Three-Path Cross Site of Grace, where you met Hornsent for his questline, and head toward Castle Ensis. Past the Ellac Greatbridge, head south then left at the fork in the road near the graveyard. Heading southeast now, you will reach a cliffside and the Pillar Path Site of Grace.
Thiollier is sitting on a rock to the east, and when you talk to him, he will tell you about his poisoning skill. This first interaction will unlock him as a merchant, so grab anything that looks good to him. There’s not much else to do with him now, so you can head out after you peruse his wares,. If you want to follow his questline directly, return to Moore at Main Gate Cross. He will give you Black Syrup and tell you Thiollier asked him for it.
Head back to Thioller and give him the Syrup, and he will give you
Thiollier’s Concoction in return. Now that you have the Concoction, you can’t do anything on Thioller’s quest until the Great Rune is Broken. Maybe consider finding Charo’s Hidden Grave for some extra treasures.
After The Great Rune Shatters
Everything Begins To Change
As with other NPC questlines in Elden Ring, this questline gets put on hold until the Great Rune shatters as you approach Shadow Keep. Once the Rune is broken, head back to Thiollier for a third time to get a new dialogue with him. You will learn he’s haunted by memories of St. Trina, his patron, and wants to see her one last time.
If you’ve already been to the
Stone Coffin Fissure on the Cerulean Coast
, you can tell Thiollier where St. Trina is at this step, which will cause him to head to the Garden of Deep Purple. If you don’t know where she is, he will tell you he’s leaving to search for the deep-purple water lilies that he heard Moore talk about. He heard they bloom to the south, so that’s where he’s going.
After Thiollier leaves, you’ve got a lot of traveling to do if you haven’t already done it. Firstly, you’re going to need to head into the Fissure. Miquella’s charm sealed off the Fissure, but now that it’s broken, your way forward is clear.
How To Reach The Fissure
The Depth Of The Cerulean Coast
From Gravesite Plain, the best way to get to the Cerulean Coast is by following the Ellac River. Starting from the Castle Front Site of Grace, take the southeastern path until you reach where the Bloodfiends are fighting with Messmer’s soldiers, then take a left into the poison swamp region. Follow the path to the left, then head into the cave behind the Miranda Flower after the Vulgar Militia.
The left path here will take you to the Ellac River Site of Grace. After you reach the site of grace, keep following the river until you reach the Cerulean Coast. Platform across the rocks until you reach the ground, then head south past the Furnace Golem to the Cerulean Coast Site of Grace.
To find the Fissure entrance, head directly south towards the Map Fragment marker in the fog of war on the map. If the marker isn’t there because you’ve already unlocked the map for this region.
Head to the end of the long peninsula to the south. As you follow the path, you will pass some Spirit Worms and a ruin, and then after this, you’ll come across a huge hole. This is the entrance to the Fissure, and at the bottom of the chasm lies the Fissure Site of Grace.
Exploring The Fissure Depths
Reach The Garden Of Deep Purple
The Fissure itself is pretty big but mostly linear. If you take your time, you shouldn’t have any issues defeating the enemies here. At the end of the path is the Fissure Depths Site of Grace; after resting here, head up the stairs and jump off the top of the stone statue in front of you.
You will fall quite a ways but won’t take any damage when you land in the Garden of Deep Purple.
In the Garden, you will be attacked almost immediately by Elden Ring‘s Putrescent Knight. This boss is tough, particularly after the knight dismounts, and then both the knight and the horse attack simultaneously.
You can summon Thiollier in this fight if you want, but the key to defeating this foe is watching the time between his attacks and using them wisely. Remain patient and play slowly, and eventually, you will prevail. If this proves too challenging, check out PTOF‘s video on YouTube for the cheese strategy.
After you beat the Knight, you will find Thiollier in the back of the Garden, slumped over in a pool of purple nectar in front of St. Trina. After speaking to him, he will tell you that he’s ingested St. Trina’s poison and to leave him alone. He also tells you not to drink the poison because it will kill you.
Drink The Poison
It Will Kill You, This is Good
Ignore everything that Thiollier says, even though he is right about the poison killing you. You will need to “Imbibe Nectar” four times, dying each time and returning.
On the fourth turn, St. Trina will speak to you, telling you, “Make Miquella stop… Don’t turn the poor thing into a god…” When you return, pick up your runes again and tell Thiollier what you heard. He won’t believe you and will become angry, telling you not to speak those words again.
Once again, ignore what he says and tell him again. He will get even more angry and then say he will never forgive you. Reload the arena, then head back towards St. Trina’s cave. This time, Thiollier will invade you and come at you with every poison he’s got.
How To Beat Thiollier
Pass on St. Trina’s Message
After defeating Thiollier, go back into St. Trina’s cave to speak to him. Now that you’ve beaten him, he will be there licking his wounds and moaning about his weakness. Drink her poison two more times to get the following dialogue:
“Godhood would be Miquella’s prison. A caged divinity… is beyond saving.”
“You must kill Miquella… Grant him forgiveness.”
Talk to Thiollier a final time to pass these messages on. He still won’t believe you but will begin to question his disbelief as he succumbs to the poison. You’re done talking to Thiollier at this point, but his quest isn’t over. Keep playing the game until you reach Enir-Illim, where you will fight the final boss.
You can return to St. Trina after defeating the final boss to tell her of Thiollier’s fate, and you will find her there, wilted and dead.
You can loot St. Trina’s Blossom, which increases your max FP when you put it on your helmet.
You can summon multiple allies in this fight, of which Thiollier is one. You can summon Ansbach and Horsent if you complete their questlines and side with them. After the battle, Thiollier will sadly be dead, but you can still grab his loot. Interact with his body to pick up his Hidden Needle and Full Armor Set. While this is a tragic end to his tale, he fulfilled St. Trina’s wishes in Elden Ring: Shadow of the Erdtree.
Source: PTOF/YouTube
