Pretty disgusting game. I’ve never played it, but I’ve seen it.
I don’t think this is a case of mortal sin, but let’s take a moment to review the three conditions (from the
Catechism of the Catholic Church):
For a sin to be mortal, three conditions must together be met: “Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent.”
I don’t think a tasteless party game is grave in itself. If you were just playing the cards and not behaving in such a way as to magnify the impact, for example, making lewd remarks or gestures (Relax, I am sure you were not doing that!), then I think you are okay as far as gravity is concerned.
Full knowledge? Well, at first you did not know anything about the game. As the game proceeded, you gradually became aware that something was amiss, but perhaps hoped it would get better, or hoped that it would end soon. Probably by the end you had knowledge.
Deliberate consent? No. Clearly your participation began without deliberation or consent. As the game developed, you were in a pretty awkward position, sort of under social duress, so I think it’s safe to say you did not consent.
You should go to confession anyway. Your mind and spirit may be troubled by this, wondering what you should have done, or could have done. Tell the priest what happened, receive absolution, and that will help to restore your peace of mind.
Also maybe you can figure out what to do the next time someone talks about this game, or gets it out at another gathering. In my opinion, it would be pretty cool to politely voice your objections. You are probably not the only one who regretted playing. Someone is going to respect you if you speak up for what’s right.
May the Holy Spirit assist and guide you always toward a life of peace and love.