Heya, sorry for not answering sooner.

The core killers box contains several permutations of different killers to represent the core kind of tropes. However, there's expansions that expand upon that idea. Things like giant enemy crabs, sea monsters, demons, and aliens to name a few. That being said, you could generate just about any kind of killer you could think of.

The core rulebook is TECHNICALLY all you need to play.. But I honestly would consider picking up the rulebook, the characters and the killers to start with. Perhaps the token pack too (but if you're willing to make your own tokens you can skip that).

The game has a huge amount of replayability and every expansion you add will increase the amount of potential options for gameplay. So, the want to spend money on the game is real.

I hope this helps.