Gehenna is unique variant of the shishkebab, a flaming melee weapon, which sets the target on fire upon impact. Although it appears to run on fuel from the tank on the player's back, it actually requires no fuel at all.
In comparison to the standard shishkebab, Gehenna has a more pronounced and brighter flame, the valve is blue instead of the standard red, its handle is black, and the motorcycle gas tank is more aged with a green tint. Gehenna inflicts greater damage/DPS and its fire damage is 2.5x more damaging than the average shishkebab. Additionally, it uses fewer action points in V.A.T.S.. Its special move in V.A.T.S. is called "Back slash", which does 70% damage in V.A.T.S. at the cost of 22 action points, although it requires a Melee skill of 50.
Even though its blade is wreathed in fire, you can still apply poisons to the Gehenna's blade. The damage over time from the applied poison stacks with the immolation damage. If a character has the Pyromaniac perk and poison is applied to Gehenna, it becomes one of the most damaging melee weapons in the game.
When Gehenna is equipped, an oven mitt appears on the right hand of the player and their companions, as protection from the heat.
As it is constantly on fire, Gehenna will set off gas leaks if the player walks through one with the sword drawn. The same applies if a companion has it equipped.
When a limb is severed by Gehenna while on fire, the flames will never go out.
There are twelve marks etched in to Gehenna's gas tank, indicating the amount of the previous owner's kills, similarly to that of Ratslayer.
Behind the scenes
Gehenna is a valley located outside ancient Jerusalem, and was a place where various pagans sacrificed humans by throwing them in fire, and later, as Jerusalem and Judaism developed, waste would be burned there. Due to the increasing population, and thus waste, the fire was said to burn continually, and Dante used this to produce an image of hell, which is now the most widespread representation: "A place where evil people go to burn for eternity".
Gehenna is Aramaic for "lake of fire".
PCPlayStation 3 Sometimes when switching Gehenna out for a hot-keyed weapon, the tank will remain on the players' back.
PC Sometimes when you switch between the 3rd person view and the 1st person view, the flames don't appear. Removing and re-equipping the weapon fixes this problem.
PlayStation 3 When used by companions, the blade and tank will not appear, only the oven mitt on the right hand will appear.
Having Gehenna drawn in third person, and diving into water, will cause the flame to go out for a second and light back up, even though the player is underwater.