Spirits

Spirits are the remains of a deceased bug given visible form. They are only visible in-game after acquiring the Dream Nail. All Spirits, except for the Traitors' Child, can be consumed by hitting them with the Dream Nail to acquire 1 Essence; however, this does not count towards completion and the Essence is not necessary to fully awaken the Dream Nail.

These Spirits are dream-made entities who take the shape of a bug who has passed away. As such, most of them seem to be under the assumption that they are living as the bug in question. They are all encountered floating above or near the real bug's deceased body, thus many of them can be encountered in graveyards, such as the Resting Grounds. Almost all of them do not move from their spot, and offer dialogue when interacted with.

Trivia
 * Spirits were a reward tier in Team Cherry's Kickstarter campaign for AU$ 150:
 * "Ancient Wanderer: Appear in-game as a bug spirit in the Glade of Hope! Help create the appearance and dialogue for your spirit counterpart: Tell of a previous life, aid the Hollow Knight on his quest, or taunt him as he passes by."


 * If the Defender's Crest Charm is worn while in Poggy Thorax's secret room, a large number of hungry flies swarm around the Knight.
 * If Cloth's side quest has been followed, she shows up in the Queen's Gardens to help in the fight against Traitor Lord. The fight ends with Cloth and the Lord's demise, and Cloth's spirit can be seen and spoken to upon leaving and re-entering the room where the fight took place.
 * Dr Chagax's name might be a reference to the Brazilian Bacteriologist Carlos Chagas, who discovered the self-titled Chagas disease. This disease is spread by the Triatominae insect, also known as the Kissing Bug, which the spirit itself resembles.
 * Caelif & Fera Orthop might be named after the Caelifera suborder and the Orthoptera order of insects, which includes grasshoppers.
 * Waldie's design and dialogue may be a reference to the Berserk series. Their one open eye, single arm, and large sword are very similar to the main character's design, and 'you wouldn't have the guts to face me' mentions the main character's English name, Guts.

References

Fantasmas Призраки Fantômes Duchy