Idus Martii is a hidden role game for 5 to 8 players.

According to Plutarch, a seer had warned that harm would come to Caesar no later than the Ides of March. On his way to the Theatre of Pompey, where he would be assassinated, Caesar passed the seer and joked, "The Ides of March are come", implying that the prophecy had not been fulfilled, to which the seer replied "Aye, Caesar; but not gone."

Players are members of the Senate who must plot in favor of or against the magnicide of Julius Caesar. But it is not that easy, as they need to identify who shares their convictions in order to partner against the other players...whilst keeping a look out for those only looking to fatten their purse.

There are four roles that are dealt each turn:

• The "Consul" decides who plays in the round by assigning the other roles. The Consul is passed in clockwise order at the start of each round.
• There are two "Edils" who vote, secretly, whether Caesar should live or die.
• The "Praetor" sneaks a peek at one of the two Edils’ played vote cards and may then force them to exchange their card.

These two votes are then shuffled, revealed and their results will either move the ‘kill’ or ‘save’ caesar token up the track. The game ends once everyone has played the Consul twice. Then players reveal their role card, total votes are tallied and Caeser either lives…or dies.

But the decisions are not that easy. At the beginning of the game, players are dealt two faction cards (either in favour, against or neutral to “magnicide”) and must discard down to one mid-way through the game… keeping all players on their toes!