@nprofile1q... it's a just a card game, not a collectible card game like Magic or Pokemon. There is an.expansion to let you play with more people.
It's a.kind of twisted rummy. You have to build sets of cards, but instead of laying the sets down in front of you, they are discarded to draw another type of cards.
This is where the Cthulhu/backstabbing comes in. The second type of cards are monsters and have effects that force others to discard or let you steal.cards.
https://boardgamegeek.com/boardgame/200371/necronomicards