Folly

"Once a highly intelligent bug, inflated by the misuse of soul. I've heard whispers that the secret these fools were searching for was immortality. To live forever... I've never heard of anything so obscene!"

Follies are enemies in Hollow Knight. They used to be scholars of the Soul Sanctum, but their bodies became inflated after the Sanctum's failed Soul experiments.

Behaviour and Tactics
Appears out of thin air, homing in on the Knight and dealing contact damage.

Soul Warriors also summon them in the Soul Sanctum as well as in Colosseum of Fools, making it difficult to heal during these encounters.

Location
They can be found in large groups across the Soul Sanctum, usually appearing in the air. They are also spawned by Soul Warriors in their fight in the Soul Sanctum, the Colosseum of Fools and Godhome (Ascended Version and higher)

References

Блажь Folly Głupik