Gehenna Gate

The Gehenna Gate is a living demonic doorway between Assiah and Gehenna.

Overview
A large, macabre and ornate gateway, the Gehenna Gate can be summoned in much the manner of a familiar, using the blood of Satan's host or his children and a chant. Its primary purpose is to allow passage between Assiah and Gehenna.

The gate can be dispelled by attacking a certain weak point (An eye in the manga, a heart in the anime) located at the top of the arch.

Powers and Abilities
Dimensional Travel: The Gehenna Gate, whilst being a living thing, tends to serve purely as a gateway between Assiah and Gehenna. Once it has been given a target with which to travel, it appears that the gate will not release its charge until the journey has been completed, as Satan noted it does not give up something once it has taken hold.

Independent Motion: In the anime, it was shown that the Gehenna Gate could move from the place where it was originally summoned, allowing it to fly through the air.

Living Statues: In the anime, the statues that flank the Gehenna Gate were shown to be Demons in and of themselves, charged with defending the Gate from Attackers. They were physically quite powerful, able to throw off a normal attack by Arthur A. Angel. They could also fly and breath fire.

Trivia

 * The Illuminati managed to create an ever-expanding, abiotic, artificial Gehenna Gate with their superior monetary assets and technology.
 * In the anime strong blue flames easily destroy a Gehenna gate.