This is a great question that gets me thinking about what the book might contain. This is one of those cases where it
could be adapted to D&D or Pathfinder or something similarly crunchy, but I can easily see why it would get its own system, especially since there's already the bones of an established system present in the book material.
- As mentioned, attributes deviate. Scores range from 1 to 120, with human average being 3-4. Because...
- The system itself is an artificial one in the context of the universe, with an express intention of making crawlers super-human very quickly. This is because...
- The context is that this is an intergalactic game show. One of the most important "stats" is view counts. Popularity means the show-runners want to keep you alive, benefactors give you extremely powerful equipment not found in the dungeon, and, if you're "lucky," the system AI that keeps things running could develop enough of an interest to not kill you for funsies. Any Dungeon Crawler system worth its salt should heavily incorporate this as a mechanic.
- A frankly insane bestiary with a a slimmer overlap with standard RPG tropes than you'd think
- A spell list with loads of unique spells, in a system where almost all crawlers can cast spells to some extent, regardless of class
- Speaking of it being an artificial system - it borrows MMO-like elements as well. In addition to a spell point system, cooldown mechanics run rampant. There's a cooldown on consuming potions, for instance.
Some folks have spoken about breaking the rules/system/game. That is a massive theme of the books, but I wouldn't weigh that too heavily as an imperative. Players won't be playing Carl, they'll be crawlers in the system. They can choose to try to break the game, or just try to survive. Honestly, if this game does it right, PCs will be getting so many wild magic items with weird potential interactions that they'll be finding ways to break things not because they have to, but because it's
fun. The DM, as always, will have their work cut out for them.
If the game does things wrong, it'll just use a system similar to one they've already done for a different IP, and make it Carl-themed.