How to complete the Thiollier quest in Elden Ring: Shadow of the Erdtree

The Elden Ring Thiollier quest is one of the more important ones you'll encounter among Miquella's oddball companions, relating as it does to St. Trina and her connection to Miquella. In case you don't remember, or are a person with a normal amount of Elden Ring lore in your brain, St. Trina is the goddess of sleep and at this point, it's basically confirmed that she's an alter ego for the Empyrean Miquella.  

Thiollier is a worshipper of this saint of slumber but with Miquella casting off his various bits around the Land of Shadow, he wants to determine the fate of St. Trina and drift off into a peaceful eternal slumber. Here I'll explain each step for completing Thiollier's quest in Shadow of the Erdtree—be warned, this guide will include spoilers for his questline, particularly in the final section. 

Elden Ring Thiollier quest steps

Thiollier's quest is one of the most important in the game, revolving around the mystery of St. Trina and Miquella. While not all of these steps are necessary, this will give you all of the dialogue in Thiollier's journey:

• Talk to Thiollier at the Pillar Path Cross site of grace in east Gravesite Plain
• Get the Black Syrup from Moore at Main Gate Cross and deliver it to Thiollier
• Ask Thiollier about the Black Syrup and tell him you're weary of life to get Thiollier's Concoction
• Head to the Shadow Keep to break the great rune and dispel the charm
• Talk to Thiollier again to find out he's heading to the Southern Shore
• Enter the Stone Coffin Fissure at the southernmost point of the Southern Shore and traverse the area
• Summon Thiollier in the arena and defeat the Putrescent Knight boss
• Talk to Thiollier in the Garden of Deep Purple after the boss and imbibe the nectar
• Tell Thiollier what was said twice, defeat him when he invades in the Garden of Deep Purple, and then repeat the words to him again
• Summon Thiollier in Enir-Ilim and the final boss to collect his armour set and weapon afterwards

Where to find Thiollier

You can first find Thiollier at the Pillar Path Cross site of grace in the east Gravesite Plain. To get here, you'll need to head across the Ellac Greatbridge, then go south-east through the Messmer soldier camp in front of Castle Ensis and continue along the road. When you reach a fork, take the left road that makes its way towards a Miquella Cross just ahead—you'll find Thiollier sitting on a rock next to it. Thiollier doesn't have much of note to say at the beginning, but he will sell you poison items, including the Deadly Poison Perfume Bottle weapon.

Delivering the Black Syrup and Thiollier's Concoction

Once you've met Thiollier, you should go to the Main Gate Cross site of grace outside Belurat if you haven't already, and talk to Moore there. This merchant will give you some Black Syrup to deliver to Thiollier. If you ask him about the mysterious syrup, he'll tell you that he can make you a nice drink if you grow weary of life. 

Tell him "I'm weary of life" and you'll get the Thiollier's Concoction consumable plus unlock the ability to purchase it from him. As far as we can tell, Thiollier's Concoction doesn't serve a purpose in the quest, but I'd stock up on a few of them in case a purpose is discovered for it later beyond simply killing you when you chug it down.

Traveling to the Southern Shore

After you arrive at the Shadow Keep in Scadu Altus and get the message about the great rune shattering and the charm being dispelled, Thiollier will have new dialogue. Initially, he won't tell you he's going to the Southern Shore, but if you rest at the grace and speak to him again, he should mention that he's heading off on the hunt for St. Trina. 

If you haven't been to the Southern Shore yet, here's how to get there:

• From the Castle Gate site of grace in the Messmer soldier camp on the east side of the Ellac Greatbridge, travel east sticking to the cliff until you reach a soldier peering out over a cliff ledge
• Drop down near where he's standing and descend the platforms to the bottom of the ravine, before heading into the cave behind the Miranda Flower to find the Ellac River Cave site of grace
• Exit the cave on the other side, head left, jump across the rocks with Torrent, and descend down the river to the Southern Shore area

It's a fairly long route, but from that point above, there's only one direction to go to reach the Cerulean Coast site of grace. The map fragment is just a little further south. To find Thiollier, you'll want to head down the peninsula towards the southernmost point, where you'll discover a big cave you can use to descend into the Stone Coffin Fissure.

Crossing the Stone Coffin Fissure and making the jump

Now, this area is a bit tricky. There's only one direction you can go in, but the route is plagued with Blood Fiends, Gravebirds, and those ruin sentinel ball enemies that will fire lasers at you from a distance, so you have to move from cover to cover. If you reach the far side, you'll find the Fissure Waypoint site of grace.

After that, you'll have to fight a Misbegotten Crusader, before reaching the Fissure Depths site of grace. The good news is that you've basically caught up with Thiollier now. When you're ready to fight a boss, go up the stairs ahead to the front of the coffin and hurl yourself into the abyss—you know FromSoftware loves a long drop into a boss arena.

How to beat the Putrescent Knight

Though not as tough as the expansion's hardest bosses, the Putrescent Knight might still give you a bit of trouble due to his high damage and some of his trickier attacks. Once you do drop into the arena, look for Thiollier's summon sign nearby. 

In terms of beating the Putrescent Knight, here are some things to watch out for:

• Bring some frost resist if you don't want to get caught out by frostbite and lose a load of health. While he shouldn't be hitting you enough to proc it, there's no harm mitigating this by boosting your robustness with the Stalwart Horn Charm or some Invigorating Cured Meat.
• The Putrescent Knight has two attacks to keep an eye on. In the first attack he cartwheels towards you with his blade, and while this is easy enough to avoid, the first two times he does it his horse will emerge and try to stomp you immediately after. The second attack is when he rises on a pillar of sludge into the air. At this point he's about to release an AoE flame attack, so get some distance.

Otherwise, it's relatively easy to split his aggro, especially if you summon Thiollier; just make sure you're mindful of his attacks due to his wide swings. After you've defeated the boss, you can activate the grace and head into the cave beyond for a fun surprise.

How to imbibe St. Trina's nectar

You'll find Thiollier in the next room alongside the abandoned St. Trina. He'll be luxuriating in the poison of eternal sleep and trying to doze off. If you interact with St. Trina, you too can 'Imbibe the nectar', though doing so will kill you. Thiollier will also start to get cranky at his inability to take a nap. So, what do you do?

You need to imbibe the nectar of St. Trina four times in a row. Upon doing this the fourth time, she'll whisper you a message. While you can relay this message to Thiollier straight away, I suggest you imbibe the nectar two more times for additional context about what she said. Thiollier will be a bit jealous when you pass on St. Trina's words to him. Repeat the message and he'll swear to never forgive you—don't worry, this is all part of the quest.

Thiollier invades in the Garden of Deep Purple

If you go and rest at the Garden of Deep Purple site of grace after this, a jealous Thiollier will invade to murder you. Thiollier has a lot of poison up his sleeve, but you shouldn't have too much trouble smacking him around, which will get you the St. Trina's Smile talisman that grants increased attack when you proc sleep nearby. Back in the cave, you'll find an injured Thiollier, who'll ask one last time if what St. Trina said is really true. Again, tell him what he doesn't want to hear and he'll curse you before falling into a deep slumber.

Summoning Thiollier in Enir-Ilim and the final boss

Now you're ready for the last part of Thiollier's quest; you've just got to complete the rest of the expansion first. When you arrive in Enir-Illim during the main story, you'll be faced with an important confrontation. If you've completed Thiollier's quest as far as the previous step, you'll be able to summon him to help in the fight, during which he'll drop some special dialogue about serving St. Trina. 

After the fight, you can summon Thiollier for the final boss just in front of the door into the arena next to the Divine Gate Front Staircase site of grace. Whether you summon Thiollier or not, after the boss, look for his body in the arena to get Thiollier's Armor, which boosts arcane, and the special Thiollier's Hidden Needle fist weapon that deals eternal sleep buildup and does magic damage. 

Also be sure to make your way back to St. Trina to get the St. Trina's Blossom from her body; this little flower you can wear boosts max FP slightly.  All's well that ends well… right?