There are a few side quests to pick up for some of the NPCs in Hollow Knight Silksong, and one of the quests you get is the Flexile Spines Wish Quest. This quest will take you around the map to locate an elusive item called Spine Core, which is dropped by a particular enemy type. This guide will detail where to get Spine Cores in HKS.
How to Collect Spine Cores in Hollow Knight Silksong

While dealing with Hokers, hit them once to release their Spines, then hit the Spines to get Spine Cores. Hokers are defeated after 3 strikes, giving you limited chances to obtain Spine Cores if you hit them repeatedly early on. Additionally, the Spines that drop by the Hoker land in different directions will disappear after a while. It is best to run around and locate them all, then hit them to collect Spine Cores.

To identify a Hoker, look for an enemy that appears as a green, airborne ball of moss. It has a visible skull embedded in its center and is covered with several needle-like spines protruding from its body. These enemies usually hover in the air, so either jump up to attack or wait for them to float closer. Hit them once to release the spines, wait for the spines to reappear, then hit them again. Each hit reduces the number of visible spines, and after the third hit, the Hoker is defeated.
To locate Hokers, just head to the right side of the Seamstress’s home in Far Fields, and you will spot two Hokers within this level. They respawn if you leave the level and return, helping you farm all 25 Spine Cores for the quest.
Flexile Spines Quest & Unlocking Glide In Hollow Knight: Silksong

Interact with the Seamstress in Far Fields to get the Flexile Spines quest, where you are required to collect 25 Spine Cores from Hoker enemies. The Seamstress is located at the lower levels of Far Fields, keep going downwards till you get to an open field. Once you get to this point, start going upwards to find a balloon-like building. Head inside to talk to the Seamstress, who requires Spine Cores for the quest.
After collecting the required Spine Cores, return to the Seamstress and hand her the required items. In return, she will gift the Drifter’s Cloak item, which is especially useful for exploration. With the Drifter’s Cloak equipped, you get to glide after jumping and chase wind currents to take you further. Hollow Knight Silksong offers a few boss challenges like The Savage Beastfly and Moss Mother, so check out our guides on those too.