We have to talk about Thaddeus. Maximus’ former friend from The Brotherhood of Steel in started out as nothing more than a comedic side character, but his choice to take a strange yellow “healing potion” sent things down a dark path. In the episodes that followed, we’ve seen him survive an arrow to the neck, develop a wrinkled appearance, grow an odd mouth on his shoulder and—most recently—lose his entire arm.
But is he truly just turning into a Ghoul? After all, he still has his nose. Some fans argue he might be transforming into something far rarer—and far more terrifying. Below are all the theories about what his final form could be.
Spoiler Alert! Details from Fallout Season 2, Episode 7 ahead.
3. Ghoul
This is the most straightforward possibility. We’ve seen what Ghouls look like thanks to Cooper Howard and Thaddeus’ group of child workers, and Thaddeus seems to be well on his way there. He even believes this theory himself. “I’m guessing you already know, but I’m pretty new to this whole ghoul thing,” he tells the Ghoul in Season 2, Episode 7. “Still have my nose. That’s the worst part, honestly—just waiting for it to drop off.”
He then shows off the mouth growing on his side, but the Ghoul clearly doesn’t see this as normal. So while Thaddeus being a Ghoul makes the most sense, plenty of clues point to a different outcome entirely.
2. Super-Mutant
Many fans quickly noticed parallels between the potion Thaddeus drank and , the artificial virus that creates Super-Mutants—creatures present in every Fallout game but absent from the series until Season 2, which featured a brief cameo from .
Could Thaddeus be mutating into a different kind of mutant altogether, not a Ghoul? That would certainly explain his unusual mutations—like losing entire limbs before his nose falls off, which is supposed to be one of the earliest stages of change.
3. Centaur
This theory builds on the previous one—humans exposed to F.E.V. become mutants, but when humans and animals are tossed into F.E.V. vats, they become “centaurs”: bizarre hybrid beasts with misshapen legs (or even arms used as legs) and no arms at all. The biggest clue here is clear: Thaddeus loses his arm in Season 2, Episode 7, which isn’t typical of any “standard” mutation.
But if centaurs are made by mixing humans and animals in F.E.V., how could Thaddeus become one? The leading theory is that the potion Thaddeus took wasn’t just F.E.V.—it was F.E.V. already infused with other creatures’ DNA. That’s the risk of buying strange stuff from shady dealers: you never know what you’re getting.