No, i think the JoD is real, not in-game. More along the lines of:
"I need +3 to hit that ogre!"
"Try the JoD, dude!"
"Okay!" Pulls slip from jar. Reads. "What?! I hit, doing double damage but my weapon breaks off in the target?! Noooo!"
"Dude, they don't call it the Jar of Doom for...