Dark Spirits (闇精霊 Yami Seirei), also known as Larva (ラルヴァ Raruba), are the creatures residing within the Red Night. They were inadvertently summoned by Lieselotte Werckmeister when she tried to destroy the world.
Larva, as their name implies, are the creature representing Larva, the magical element of Void and Darkness. They are originally the negative energy of Ayamegaoka given forms by Lieselotte's Specialized Bounded Field: the red night of Phantasmagoria. Their purpose is to kill off every single humans on the planet, so that Lieselotte can create her desired world. Due to the massive amount of energy that dwells beneath the earth of the area, the number of Larva in Ayamegaoka is literally endless and can possibly multiply even more when Lieselotte's spell reaches its peak, which will trigger a Larva outburst of enough magnitude to cover the entire world as she planned.
The Larva have shown to change their form gradually over the course of the story. Below are the list of forms they have taken. The names are based on the their appearance.
The blob Larva is the first type to appear in the series. They have a human face, but the main body is blob-like and seems to be unstable. Their other limbs are two transparent tentacles, which can burn human skin upon contact, angelic wings whose number varies differently for each individual and a metallic-looking black halo over their head. They also have strange white plates in the area around their head. In terms of size, they are slightly taller than a human. This type of Larva moves quite slowly and can be easily dispatched. Despite this however, they are still quite resilient and pose a danger to normal humans.
Flight-type Larva started to appear after the first Black Knight Gula's death. Their appearance are not very different from the first type, but their wings have evolved enough to make them fly. Some Larva now have two instead of one face and the white plates take on human's features. Their number of tentacles varies from three to four instead of only two. Their overall form also looks more solid compare to the previous version.
The insectoid Larva appeared after the second Black Knight Acedia's death. They are basically an upgraded form of the flight-type, but their power has significantly increased. While retaining all the strength of its predecessor, this type of Larva is much faster, more agile and deadly. Their appearance are also vastly different from the previous flight-type. Their size seems to have sunken a little; their head has evolved into a large sting while one of the tentacles has become a tail.
Humanoid from is possibly the last stage of evolution for the Larva. They appeared after the third Black Knight Ira's death. They are no longer able to fly like the insectoid Larva can, but they can put up a quite hard fight, even for someone as strong as Misuzu Kusakabe. They now take on female humanoid form with a white tail growing out from the back of their neck and a long sword from their wrist. In this state, their fighting capabilities much resemble that of a human and seem to show some sign of intelligence.
In Resona Forma, Before Story arc, Lieselotte introduced a new type of gigantic Larva, each of which is at least 20 meters in height. They seem to mainly act as a swarm host, summoning smaller Larva to overwhelm the opponent with sheer number. Despite their collossal size, they can regenerate, although at an extremely low rate compared to other types.
- In the anime, only the blob and flight-type Larva are present, one of which is never fought.