How many of the treasure trove cards are expansion specific? I'm back and forth about the crimson outlaws expansion
None of the TT cards interact exclusively with the Crimson Cutlass -- a few require the Last Adventurer or CTHB. That said, while the Crimson Cutlass is optional, I'd consider it a must-have if you're playing a 4-5 player game, as it adds some serious tactical choices in where to go. Plus the Sinister Motivation cards should add some great gameplay whether you use the CC island or not.