The seal is comprised of Hashirama Senju's cells and must be surgically implanted into a compatible vessel, a process which drains a great deal of the caster's vitality, shortening their lifespan. The seal itself acts as a gateway to a separate dimension that Tanuki called the underworld (異界, ikai), wherein dwells a legendary beast named Nue that is born the moment the seal is completed.
The mark acts as a medium for absorbed chakra to be transferred into the Nue, nourishing it, as well as a gate through which it can be summoned. It also allows the user to create snake-like creatures out of dark chakra, which can be used in battle or parasitically attached to individuals suffering from negative emotions to continually drain their chakra, further disturbing their mental state. As Nue is fed chakra, the seal's pattern spreads and the beast quickly grows into a gigantic monster, eventually becoming a living chakra bomb that can be summoned to a location and detonated, creating an explosion large enough to destroy an entire city.
As the true source of power for this technique is negative emotions, if the vessel overcomes these emotions the seal will be destroyed. When Sumire Kakei achieved this, a portion of the seal remained and migrated to her palm, allowing her to maintain her symbiotic bond with Nue.
The technique's name comes from Gozu Tennō, a Japanese deity of pestilence.