Keeping your king safe when the rules keep moving

Whatever the cards do to the board, the game still ends the same way it always has. Your king is attacked, it can't get out, and you've lost. Checkmate hasn't changed. What's changed is the number of ways to reach it. In ordinary chess, every attack on a king comes one move at a time, along lines you can see coming. In Built Deck, a king can be teleported next to, rotated into a corner, attacked twice in a turn, or replaced for a turn by a pawn standing on f5. This article is about the new ways a king dies, and the cards and habits that keep it alive.

The attacks that don't look like attacks

The first thing to unlearn is that a safe-looking king is safe. Three families of cards move pieces without moving them, and each one can put an attacker next to your king in a single card.

The teleports move a piece along a line it already stands on: Horizontal Teleport along its rank, Vertical Teleport along its file, Diagonal Teleport along a diagonal, and Queen's Teleport along any of the three. A rook on a1 can arrive on a8 without passing anything in between. If your king is castled behind pawns, look at the lines that lead to squares beside it, and ask what's standing on those lines anywhere at all.

Move Opponent Piece is the reverse and worse: for three Braincells your opponent moves one of your pieces to any empty square. The defender you were relying on can be lifted out of the castle and set down on the far side of the board. Swap Theirs and Swap Any do a version of the same thing by exchanging two pieces' positions.

The rotations move everything. Rotate 90° Right and its five siblings turn the whole board; the ring and quadrant cards turn parts of it. After a rotation, your king is somewhere new and so is everything that was attacking anything. Before any rotation card is played, the position has to be read as if it were a fresh board, because it is one.

The defense against all three is the same, and it's a chess habit rather than a card: count the attackers, not the distance. Ask how many of their pieces could reach a square next to your king if distance didn't matter. If the answer is two or more, the king is not safe, however far away they are.

Two moves in one turn

A single move rarely mates a king that has a flight square. Two can. Move Again adds a move for one Braincell. Double Time adds two for three. Blood Oath adds two for one Braincell and one of the player's own pieces, sacrificed. All In adds three for two Braincells, a card, a piece and a give-back. Prisoner Exchange adds one in exchange for handing back a captured piece.

Check, then mate, in one turn. Or check, and the second move takes the only piece that could have blocked. When you count your king's defenses, count them against two moves, not one. A flight square that one move covers is not a flight square.

Extra-move turns can be undone. Countermand is an Instant that undoes the last card played, on their turn, so the Double Time is gone before the moves happen. Revert Last Turn takes back the whole turn after the fact, if you're still in the game to play it, which is the point of the last stand.

The last stand

Checkmate isn't always the end. If the mated side has a card it could play, a draw still to be dealt or a playable card in hand, it gets one more turn to find a way out. Still mated after that, it loses. This is the last stand, and it's the single biggest difference between a chess king and a Built Deck king.

It means two things. For the defender, a card in hand is a life. Revert Last Move, Homecoming to send all your pieces home, Swap Yours to put a different piece where the king was: any of these is a way out if it's in your hand when the mate lands. For the attacker, mate on a board where your opponent holds cards is a threat, not a result. Before you commit to a mating attack, look at how many cards they hold and what their deck has shown you. If they've got five cards and a known revert, mate once and expect to need to mate twice.

The king that isn't the king

Four cards make another piece the king for a turn. A New King picks whatever opponent piece stands on f5. Surprise Coronation picks c6, Puppet King d3, Royal Decoy e6. For the rest of your turn, the game treats that piece as their king. Attack it and it's check; trap it and it's mate. Once the designated piece is gone from the board, the real king is the king again.

As the defender, the lesson is about those four squares. A pawn on e6 is a pawn, until it's your king for a turn and it's sitting in the middle of the board with no defenders. Don't leave a lone piece on f5, c6, d3 or e6 when your opponent has Braincells to spend and you don't know their hand. As the attacker, these cards are a way to mate a king that has castled behind a wall of pawns without touching the wall. Find the piece they left in the open, and crown it.

Making the king move like something else

The Royal cards give your own king another piece's movement for a turn: Royal Queen for four, Royal Rook, Royal Bishop and Royal Knight for three, Royal Pawn for one. These are escape cards. A king that can move like a knight for a turn jumps out of a net that was built for a king. They're also, rarely, attack cards: a king that moves like a queen can take the piece giving check from across the board. Keep one in a deck that expects to be attacked, and keep it in hand rather than playing it early.

Mines and the king

Two traps end the game outright. A Landmine destroys the first piece to step on it, and a king that steps on one loses. A Claymore is aimed at a square beside it, and a king that lands on that square loses. A Spike Pit destroys an enemy piece but a king steps over it unharmed.

So a king walk across squares your opponent could have mined is a different kind of risk from a king walk across attacked squares. You can see attacked squares. You can't see the mine. If your opponent has played a face-down trap and your king needs to travel, Disarm first, or send a piece you can spare across the same squares ahead of it, or play Probe on the square you most fear. A king is not a piece to gamble with against a hidden trap.

What actually protects a king

Putting the defenses in order of how often they save the game:

1. A card in hand. Any playable card buys the last stand. Don't empty your hand when the king is under pressure.
2. A flight square that survives two moves. Keep a square beside the king that no single move and no obvious card can cover.
3. Flash Shield. An Instant that protects one of your pieces from capture until after your next turn, played on their turn, after they've shown the attack. Put it on the defender their combination has to remove first.
4. Guardian Ward, which protects a piece until it next moves. On a defender that intends to stay put, that's a long time.
5. Flash Freeze, played on their turn on the piece that was about to deliver the check.
6. Wall, built on the square the attack has to come through.
7. Iron Wall, which protects every piece except the king. It won't stop mate, but it keeps the defenders alive long enough to matter.

Notice what isn't on the list: more pawns in front of the king. Pawns stop pieces that have to travel. Against teleports and rotations, they're scenery.

A last note on your own attacks

Everything above cuts both ways. Their king is as exposed to teleports and extra moves as yours. The turns that win games are the ones where a card and two moves arrive together, against a king whose owner counted attackers by distance. Build those turns, and before you play one, look at their hand size and ask whether the mate will stand.