Joe Manganiello, best known for his role on True Blood and for his cameo as Deathstroke in the Justice League post-credits scene, appeared on The Late Show with Stephen Colbert to discuss a topic very close to his heart -- Dungeons & Dragons -- and to throw a little shade.

A fan of the role-playing game since childhood, Manganiello proved his own nerd cred with a profile of the character he's now playing, going into some detail with accurate D&D terminology and lore. Colbert, who had some experience with the game as well, managed to keep up with the jargon: "You don't come into my house and drop Tiamat and think I'm not gonna drop Bahamut!"

Manganiello seemed impressed, enough so to invite Colbert to his house, with its basement modified into a gaming room, complete with dragon heads mounted on the walls, for a game of D&D. The two even pulled out a set of polyhedral dice to roll some character statistics during the interview.

When the name of another famous nerd came up, however, Manganiello had some doubts. "Vin Diesel plays," said Colbert. "He says he does."

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"He does," Manganiello replied with a mischievous smirk, "but I don't know anyone who plays with him ... and believe me, I would know! I would know."

While it's difficult to argue with Manganiello's clear authority on the subject, Diesel has long been beloved by nerds for embracing D&D in spite of his tough, action hero image. Fans can probably agree on one thing, though: The best way to settle this would be for both actors to join a new game together. Manganiello has the ideal space for it, after all.

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