Yep, some decks do add extra major arcana beyond the usual 22. Tarot cards are printed on big sheets that can fit around 80 cards (an 8x10 grid), so there's often space to throw in extras.
A few examples off the top of my head:
- The Happy Squirrel popped up in a bunch of indie decks after it appeared as a joke on The Simpsons, lol.
- Zeke's Arcana added a "Patron" card.
- There's a Native American / Indigenous deck out there with two extra majors.
- Lots of other decks tack on extra majors to suit their theme or vibe.
So yeah, it's totally plausible someone made a deck with a 23rd card called "The Unknown" or something similar. Creators do whatever feels right to them. That said, the traditional tarot structure only has 22 Major Arcana cards — that's the standard across most systems.
