The School of Architects: Introductory Level
The rules for two players are identical to those used for solitaire play, with the following exceptions:
Place the Champion of the Oniverse card nearby.
Each player builds her own castle.
You may not directly place a drawn Defender tile into your partner's castle. You may, however, donate a drawn Defender tile to your partner.
To do so, you must destroy a tile in your own castle (you may not destroy a tile that has other tiles above it, nor may you destroy a tile that would split your castle into two separate structures).
Your partner receives the donated tile and must immediately place it in her castle. Then, it is the turn of the player who received the donated tile. In this way, one player might place 2 tiles in a row. Players take turns drawing and playing tiles until the game is over.
You may not donate a Traitor tile.
You must always destroy a tile in order to donate a tile. As such, you may not donate a tile if there are no tiles in your castle.
Drawing a Traitor tile counts as your turn.
When you must encounter Exam I, verify that both players have a complete foundation (6 tiles). If they do not, both players lose. Otherwise, you and your partner decide which of you will encounter the Exam.
The player who encounters the Exam must fulfill its conditions as in the solitaire game. If successful, that player receives the Champion of the Oniverse card, and the game continues. If that player failed the Exam, both players lose.
When you must encounter Exam II, it is the player who does not have the Champion of the Oniverse card who must encounter the Exam. If successful, she receives the Champion of the Oniverse card from her partner, who will be responsible for encountering Exam III. If successful, the two players win!
A player in possession of the Champion of the Oniverse card may choose to give it to her partner. To do so, she must destroy 6 tiles in her castle (you may not destroy a tile that has other tiles above it, nor may you destroy a tile that would separate your castle into two separate structures).
The Admiral's Academy: Base Level
The rules for two players are identical to those used for solitaire play, and to those used in the two-player introductory level game with the following exceptions:
In order to pay for a donation, a player may now destroy a tile that is under other tiles in her castle. If she does so, the tiles above slide down to fill the empty space. Tiles of the same shape are permitted to become adjacent as a result of this slide.
A player may not use the effect of a discarded Juggler or Pyro on her partner's castle. She may, however, donate the tile so that her partner can discard it and use the effect himself.
Tiles revealed by the Seer must be used by both players. There may be only a total of 4 revealed tiles between the two players.
If two players wish to play with The Prison rules, they build one prison together.
The Menace: Expert Level
The rules for two players are identical to those used for solitaire play, and to those used in the two-player base level game.