Here are the rules of a 2-player variant of Catan that I developed with my sister. We have tested it several times and it makes for a very enjoyable game. The game will also work with 3 players if one has the 5-6 player extension to regular Catan, although we haven’t tested it yet. We have found a few 2-player variants online in which each player controls two colours, but none quite like ours.
If there are any ambiguities in the rules please see a more detailed description at https://boardgamegeek.com/thread/2436188/coalitions-catan-2-3-player-variant-catan
THE COALITIONS OF CATAN
By Stephen Pasteris and Marianna Pasteris
To play with 2 players one needs the Catan base game and to play with 3 players one needs, in addition, the 5-6 player extension.
We have 4 clans (when 2-player) or 6 clans (when 3-player). Each clan owns its own set of resource cards and development cards. For the purposes of resource production, trading, building, playing development cards, and obtaining longest road and largest army cards each clan acts like an independent player in regular Catan (each clan having its own colour).
Each player P controls 2 clans: PL and PR.
The game ends when, for some player P, both clans PL and PR have at least 10 victory points each: player P then wins the game.
If the longest road or largest army card is owned by one of Player P’s clans then the card gives both PL and PR one victory point each.
Resource cards are face up whilst development cards are face down. For a player P, PL’s cards/pieces and PR’s cards/pieces are on the left and right of player P, respectively.
Placing the initial settlements and roads is as in regular Catan. The sequence in which the clans place the initial settlements and roads is:
AL, BL, AR, BR, BR, AR, BL, AL for 2-player
AL, BL, CL, AR, BR, CR, CR, BR, AR, CL, BL, AL for 3-player
Where A, B and C are the players.
In the main game, both of a player’s clans trade and build on the same turn (i.e. turns alternate between players rather than clans). Player P’s turn breaks down as follows:
1) Resource production:
Player P rolls the dice for resource production as in regular Catan. Note that, for the purposes gaining resources, each clan acts like an independent player does in regular Catan. If Player P rolls a 7 then he/she moves the robber as in regular Catan: the stolen card can be given to either PL or PR (Player P chooses)
2) Internal trade:
If both PL and PR have at least 1 resource card then Player P can choose 1 card from each of PL and PR and swap them. i.e. Clan PL can trade any one resource card for any one resource card of Clan PR. At most one such trade can happen at this stage.
3) External trade:
Clans PL and PR can both trade with the bank or harbours as in regular Catan. Note that clans cannot trade with each other at this stage. Clans belonging to different players can never trade with each other.
Clans PL and PR can remove as many cities/settlements/roads as they like, as long as when one clan removes a road one end of that road must not touch any other road, settlement or city belonging to that clan (it is ok for it to touch buildings and roads of other clans). Any removed pieces go back into the pile of unused pieces so can be used again in the future.
Both clans PL and PR can build or buy development cards as in regular Catan.
Either of clans PL and PR can play at most one development card at any point during Player P’s turn, as long as it wasn’t bought on that turn.
If a robber is played (via rolling a 7 or playing a knight card) by Player P then the stolen card is chosen at random: the player controlling the clan from which it is stolen hides their resource cards and cuts them. Player P (or another player if Player P is stealing from one of its own clans) is then presented with the cards face down and picks one. Note that if the robber was played by rolling a 7 then Player P can choose which clan to give the card to, whilst if it was played via a knight card then the stolen card must go to the clan that owns the knight card.
A note on the number of victory points to win:
The game ends when there is a player P in which both clans PL and PR have at least 10 victory points each (Player P then wins the game). We originally let the game end at 8 victory points each but found 10 victory points made a much more strategic game: there is more fight for land (players try to block the other player’s clans from being able to make enough settlements) and our “desertion” stage (Stage 4 of a players turn - which allows one of the player’s clans to move into the space previously owned by the other clan) becomes much more important. Because of the chance, when playing to 10 victory points, of getting a clan “boxed in”, a player can forfeit the game at any time.
Thanks to Salmon Qaisar for suggesting that, when a robber is played, a player can steal from his own clan, and how to implement this.