DC’s version of Vibranium called Promethium is a powerful substance that can channel any energy — including the willpower constructs of Green Lantern — into a weapon that can effectively take down the Justice League. It’s just too bad it’s wielded by the mercenary known as Deathstroke, or else it’d really come in handy.
Seen in action in 2018’s Justice League #43, by Christopher Priest and Pete Wood, this issue acts as the finale to this particular volume of Justice League as the best of DC’s best go toe-to-toe with Slade Wilson aka Deathstroke the Terminator. Wielding the might of his Promethium Blade and titanium staff, Deathstroke battles it out with heroes who are desperate to stop him dead in his tracks after he takes down Superman, Aquaman, and more in the blink of an eye.
Soon facing two Green Lanterns in Simon Baz and Jessica Cruz, Deathstroke has seemingly met his match on the field of battle. But after utilizing his smarts and current equipment tailored for an occasion such as this, Deathstroke proves that Green Lanterns can become anti-Justice League weapons with the right kind of help from a villain like himself. Shooting blasts of green willpower at Deathstroke, Slade easily blocks their attacks with his Promethium weapon. Saying that his sword “absorbs all forms of energy,” Deathstroke confirms that all he has to do is channel said energy into his titanium staff, redirect it at his enemies, and in the words of this highly skilled mercenary, “down goes the green team!”
A dangerous combination of weapons on their own, the fact that DC’s version of Vibranium can be repurposed to take out the Justice League without breaking a sweat is a big problem for a group of heroes that can usually deal with whatever they come up against with ease. Add in the fact that if Promethium is in play, Green Lanterns need to stay well away from any and all members of the League as they can end up being used against the team (and as shown here, themselves as well), and you have a kind of overpowered weapon that Deathstroke — and anyone who can get their hands on Promethium — can exploit in the worst way possible.
So while Promethium luckily isn’t lying around in enough quantities to make Deathstroke’s tactics something that needs to constantly be worried about, when coupled with the energy of a Green Lantern, it’s still deadly enough to matter. Green Lanterns should always steer clear of the Justice League when Promethium is around, or at the very least do their best to direct their constructs away from its debilitating reach.
