Puzzling out how to unlock Act 3 in Hollow Knight: Silksong is a tricky business. If you're trying to do it yourself, you'll likely have seen that you need to acquire a special quest from the Caretaker at Songclave, but it's not entirely clear what the exact unlock conditions are for it. Some say you have to do every quest or find every lost flea, but I'm here to get rid of any misconceptions.
Since I didn't do loads of side content, it wasn't actually too hard to pin down the unlock conditions for the Silk and Soul quest you need to complete to open up Act 3.
Below, I'll go through the exact requirements, what you need to do after, plus I'll provide a list of other quests I did and my reasoning as to why they likely don't matter, but just in case there's an outlier you need to complete for Silk and Soul.
How to unlock Act 3 in Silksong
Before I go into specifics, I first want to clarify some misconceptions I've seen about unlocking Act 3:
You don't have to do all questsYou don't have to find every lost fleaYou don't have to do every town quest (though almost all of them)You don't have to beat the final boss to acquire the Silk and Soul questNow that's out of the way, here's what you need to do:
Complete *most* of the wish wall quests for Bone Bottom, Bellhart, and SongclaveI'll go into specifics about which below because there are exceptionsMove the Flea Caravan to its final spot at the Pale Lake in the Putrified DuctsTo do this, you'll have to find 22 fleas (if I counted right), possibly also the giant flea in Memoriam, Kratt in Greymoor, and Vog, once the caravan has arrived in the Putrified Ducts (though this last may be unnecessary)You'll also have to find the Pale Lake and tell Fleamaster MooshkaCollect the Architect, Conductor, and Vaultkeeper melodies and gain access to the final boss in The CradleUpon successfully fulfilling the above criteria:
Complete the Silk and Soul quest which you get from the Caretaker of SongclaveDefeat Grandmother SilkIf you fulfill all of these requirements and defeat the boss, you'll reach Act 3.
Silksong Act 3 quest requirements
Below, I'll go through the exact quests and conditions I completed for each town to unlock Silk and Soul, plus those that I reckon are likely unnecessary.
Bone Bottom quests
Bone Bottom RepairsA Lifesaving BridgeGarb of the PilgrimsVolatile FlintbeetlesThe Terrible TyrantAn Icon of HopeAlso, make sure to fight the Skull Tyrant that attacks Bone Bottom, witness the funeral, and talk to the leader of Bone Bottom to receive the Hornet Statuette once all these quests are done.
Bellhart quests
Restoration of BellhartMy Missing CourierSilver BellsMy Missing BrotherBone Bottom SuppliesSavage BeastflyBellhart's GloryYou'll also have to complete Trail's End. This is Shakra's quest and requires you to either find (or miss) her when visiting The Marrow, Deep Docks, Hunter's March, Far Fields, Wormways, Greymoor, Sinner's Road, Shellwood, Bilewater, Blasted Steps, Sands of Karak, and Mount Fay. You'll also have to purchase the maps for these regions either when you see her, or in Bone Bottom or Bellhart depending on your progress. The Trail's End will appear in Bellhart once done.
Make sure to also speak to Pavo (bell guy) in Bellhart to receive your Bellhome in the town. It seems like you can do this before completing Shakra's quest, provided you've done the Restoration and Glory ones.
Songclave quests
Fine PinsStrengthening SongclaveThe Lost MerchantThe Wandering MerchantCloaks of the ChoirBalm for the WoundedYou'll also have to complete Final Audience. This first requires you to complete three bell puzzles to collect Cogwork Heart pieces, which you then use to revive the Second Sentinel in the lower section of the Cogwork Core. You then need to encounter her twice, randomly fighting enemies around the Choral Chambers. For me, this was en route to the Cogwork Dancers boss and in the top left near the entrance to the High Halls. After that, the Final Audience will appear in Songclave
You'll also need to complete Silk and Soul, of course. I also did some other quests that I don't think are related. For example, I completed two of the courier quests (Bone Bottom and Pilgrim's Rest), but I didn't do the delivery for Songclave or the Queen's Egg. In terms of the Grand Hunts, I didn't do the Wailing Mother (meaning The Terrible Tyrant and Savage Beastfly may not be necessary). I also didn't do any quests for Greyroot or the Huntress.
These are the other quests I did (just for reference in case doing the above doesn't unlock Silk and Soul):
Berry PickingFlexile SpinesBugs of PharloomPinmaster's OilCrawbug ClearingAlchemist's AssistantGreat Taste of PharloomPilgrim's Rest SuppliesSilksong guide: Home of all our bug-battling tips
Silksong flea locations: Gather the lost fleas
Silksong simple key locations: Where to use it
Silksong Hokers location: Support the Seamstress
Hunter's March bench: Yes there is one