In 10 minutes, it looks unworkable. You'll want shortcuts -- variants.
Some mafia variants:
-- "Vengeful": when anyone is lynched, they are allowed to kill another player. Play here should be faster, but will require more mafia for balance.
-- "Nightless": No nightkills. This doesn't sound faster but eliminates that huge suck of stopping everything at night.
-- "Locked Votes": No one can change votes. Thoughtful players take longer to vote under this strategy.
-- "Vote by Acclamation": Anyone can say "I propose we lynch A". You call "Does anyone second?" If someone says "I second lynching A," you call for a voice vote ("Yes!" or "No!"). Everyone shouts. You as host decide if the lynch occurs.
-- "Russian Roulette": Anyone can shoot another player once every day phase. The first shot has a 1/7 chance of working. The second has a 1/6 chance. The third, 1/5, etc. When someone is killed, the day restarts. (25 players may be too many for this variant.)
-- "Vigilante Votes": Everyone has one gun. There may still be regular voting.
For you I'd recommend a Nightless game with Vigilantes and/or Vengeful. You don't need Votes by Acclamation or Locked Votes, but variants that speed the game will help you. Votes by Acclamation with Vigilantes might be hilarious. ("I propose we lynch Alex!" "No you don't!" *Shoots the speaker*)
To explain the game as quickly as possible, try something like:
"This is a variant of mafia, a popular forum and group game. There are two teams, the mafia (who all know each other) and the town (who don't). The mafia win if they kill enough townies to form a majority and take over. The town wins if they eliminate all the mafia members. In this game, players die when [insert dying conditions here]. Questions?"
I hope this helps and that your game is successful and fun.
(Oh, and I hope your high school isn't weird about weapons. If you can't talk about death, killing, or guns, you can talk about "Voting people off the island".)
"The inward skies of man will accompany him across any void upon which he ventures and will be with him to the end of time." -- Loren Eiseley
I don't think there's any need to do anything that's not a regular mafia. Just handle it efficiently. Pair everyone up in groups of two, you'll go from 25 players to 12 which is much more managable for a regular mafia game. Time phases to only take a minute maximum. At the end everyone will point to who they want lynched, majority gets lynched. If there's no majority ask people if they want to change and lynch whoever becomes the majority then. Just keep reminding people that because of the limited time in your presentation they should be fast, assure them "just do something" if they still can't decide. Because no matter how efficient your set-up is, if you're gonna let people stall out every phase it's gonna take forever anyway.
But on to the set-up. Add a cupid, who makes two people a lover night 1. In most cases that limits the player total by one. Don't add too many power roles, they'll all take additional time in the nightphase to do their actions. Cop and doctor should be enough. Besides that you can add some night-actionless roles like hunter (kills a person of choice when lynched/killed, plus the extra death it causes speeds up the game) and doublevoter. Of course you could also add a serial killer, which with the extra death each night should speed up the game quite a bit in general, which allows you to spend more time on the phases.
Wow, thanks for the suggestions, everyone! I think I need a bit more time to decide exactly what I'm going to use, I sure have a lot of options now. :P I'll discuss things with my group and see what they think of everything. Once again, thank you! :)
I have noticed lately here that more and more users are playing EpicMafia. I think it would be a good idea to add our usernames on the EpicMafia list here.
Sign-ups for Brutal Host's Mafia are now open! I can't wait to see how my first mafia goes!
Prediction: "Something awesome will be taking place in the War Room in the near future..."
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