I recommend reading this thread opened by me in another Catholic forum before answering, to understand what exactly I'm asking:

https://www.suscipedomine.com/forum/index.php?topic=28067.0

Let's focus on the Werewolf part.  Summary: It is a game in which there are two teams (there are other variants but this is the basics) One is in the majority but ignores who is on his team, the other is in the minority but knows each other. The first team has to vote in rounds for someone to be eliminated, and the other team can eliminate one per turn. So far no problem. But the second team has to try to make the first team believe that they are from that team so they don't get eliminated and can eliminate them and win.

I asked if it was a sin to lie in that context. In that thread there were two types of responses: One user, although he did not respond directly, explained the Catholic concept of lies: There are three types of lies. The lie that harms others, the lie that is not harmful and can even be beneficial, and the humorous lie, for fun, the first is a mortal sin, the other two are venial sin, we must avoid all sin, even the venial ones So, all kind of lie must be avoided.

Other users responded, that it was a kind of "role playing game" in which you don't lie but you play a role and it is that role that is lying, not you, or something like that, and therefore you are not really lying. The first user did not refute this point of view, and limited himself to exposing the Catholic explanation of the lie and stressing that each one must apply these general principles to each situation.

The point is that I understand that lying is always a sin, but I don't know if those who say that in this context you are not really lying are right. At first I accepted that it was a venial sin, but now reading the thread again I'm not so clear, and I cannot ask that user directly because he is no longer in that forum.

What would be the response of moral theology to this specific context?

When in doubt, don't do it, it is not worth offending God. How many venial sins I would avoid, and how much closer to perfection I would be if only I followed that advice.

You could always ask "what would Jesus do?", or what a great saint like Jean Vianney would do.

That's what I do, I don't play it until I have a definitive answer.