If you’re diving deep into Hollow Knight: Silksong and looking to complete more side content during your journey through Pharloom, one quest you won’t want to skip is Advanced Alchemy. Tied to the mysterious and somewhat unsettling Alchemist Zylotol, this quest takes a strange turn into the arcane world of Plasmium and offers some of the most unique rewards in the game.
How to start the Advanced Alchemy Quest in Silksong
To trigger this quest, you first need to complete the Alchemist’s Assistance quest, which can be done in either Act 1 or Act 2. After finishing it, head back to Wormways during Act 3, but be aware, you’ll need a Simple Key to access this area. These can be found in multiple locations throughout Pharloom and the Citadel, so keep your eyes peeled if you’ve not grabbed one yet.
Inside Wormways, you’ll find Zylotol again, except this time, he’s undergone a rather dramatic transformation. He’s inching (alchemically, of course) toward becoming a source of Plasmium itself. Creepy? Absolutely. But also kind of cool.
At this point, you can top up your Plasmium reserves by exchanging Rosaries if needed. Then, Zylotol gives you a tool that becomes central to the next objective: the Needle Phial. With it, you’re tasked with a bloody mission … literally.
Extracting Plasmified Blood: What you need to know
Once you have the Needle Phial, descend from Zylotol’s location further into the Wormways. In this zone, you’ll face two distinct enemy types:
- Burrowers: They move underground, charge at you, and spit corrosive projectiles.
- Ceiling Crawlers: These stick to the ceiling and attack from a distance with persistent spitfire.
To gather Plasmified Blood, simply engage these enemies and equip the Needle Phial. Hold the charge button until you hear a distinct “click”, then release. This will simultaneously extract the blood and defeat the creature.
You’ll need to complete a total of 10 successful extractions. Once done, return the Phial to Zylotol to conclude the quest.
Advanced Reward: What is the Plasmium Gland?
Your efforts won’t go unnoticed: Zylotol will reward you with the powerful Plasmium Gland, one of the most game-changing quest rewards in Silksong.
This item lets you craft new Plasmium Phials at any time, removing the need to rely on natural reserves. And here’s where it gets interesting: using these Phials temporarily increases your max health and allows you to refresh tools through the Architect Crest’s “up bind” ability.
If you stack enough mask shards while buffed, your health bar can even turn blue, marking the activation of passive health regeneration. It’s a huge advantage when trekking through Silksong’s darker and more dangerous late-game areas.
Why you shouldn’t skip this quest
Honestly, this is one of those side quests that feels more like a main story beat. Between deep lore implications about Zylotol’s transformation and the mechanical depth unlocked through the Plasmium Gland, the Advanced Alchemy quest is a must-do for any hardcore Hollow Knight fan.
And hey, even if you don’t care about lore, who wouldn’t want more health and self-sustaining regen?
Explore smart, stab hard, and don’t forget to keep your Phials topped up!