Crack

A crack (クラック) 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 Helhiem by generating cracks and a Rider's Arms forms 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 tries 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 thier victims and premature Lockseeds have an unknown mutagen which transforms humans into Inves when they are consumed by them.

Appearance
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.