|This article is about a/an dimensional phenomenon in Kamen Rider Gaim.|
A crack (クラック Kurakku) is a dimensional tear in the fabric of space which connects between the Human World and Helheim Forest. Cracks can be controlled or stabilized by devices of the Yggdrasill Corporation and be used to transport researchers into Helheim. Lockvehicles can transport Riders to Helheim by generating cracks and a Rider's Armor Parts are summoned through cracks via a Sengoku Driver or Genesis Driver.
However, random cracks appear across Zawame City, which stay open for an unknown amount of time. These random cracks are a dangerous phenomenon which causes Inves to crossover into the Human World and attack civilians. An additional side effect of their appearance is the surrounding environment having various flora native to Helheim to appear in an area in proximity of the crack, occasionally including Lockseeds.
These random cracks close after a certain period of time, making an additional danger of having Inves trapped in the Human World or humans getting trapped in Helheim.
The Yggdrasill Corporation tried to conceal the existence of these random cracks by having Kamen Rider Zangetsu destroy any Inves they find, the field operatives burning all the plants in the area and presumably, silencing any witnesses who see them. The true reason of keeping this secret is to avoid panic among the citizens and prevent any potential repercussions of the company's experiments in Helheim and the Inves Games. As the Inves spread a disease that causes painful plant-like growths to appear on their victims and premature Lockseeds have an unknown mutagen which transforms humans into Inves when they are consumed by them.
Following the failed attempt by the major governments to destroy Zawame City in order to eliminate the Helheim threat, the supreme Over Lord Inves, Rosyuo, opened cracks all over the world to speed up humanity's extinction. When Kouta Kazuraba inherited Rosyuo's power as the Man of the Beginning, he chose to save humanity and preserve the world by sending all the Inves and Helheim flora on Earth through a giant crack leading to a distant planet at the edge of the universe.
Cracks resemble silver clothing zippers and even have the sound of one when opened using a Driver or activating a Lockseed in an Inves Game. Lock Vehicle cracks open and close like a flower blooming.
Cracks that open from the Sengoku Rider War Period resemble a ribbon & string like warlords wear.
Thanks to the creation of the Fifteen Lockseed, Ren Aoi is capable of creating a darker version of the natural Helheim cracks. It is visually similar to the natural ones, but the zipper was made out of human bones, and it opens up in an uneven manner.
The crack created by Another Gaim appeared to be made out of wood.
- The Cracks are similar to the anomalies from the British sci-fi series Primeval, both are dimensional tears in the fabric of space which let through hostile animals to our world.