9 Kings
(Published on 19. February 2026, 20:30 by Killer Joe)
Hello.
Normal sudoku rules apply.
Each box has a King represented by the digit that matches its box number. The digits needed to complete an entropic set and a modular set are rooks.
Entropic sets are low (123), mid (456), high (789).
Modular sets are mod1 (147), mod2 (258), mod0 (369).
(In box 1 the digit 1 is the King and 2, 3, 4 and 7 are rooks because 2 and 3 complete the entropic set and 4 and 7 complete the modular set.)
There is only one King in each row, column and box position (aka disjoint set).
No King must be in check by a rook within the same box.
Have fun.
Solution code: Row 9, first 6 digits
Comments
today, 00:42 by Killer Joe
Clarified the ruleset in the linked puzzle.
on 22. February 2026, 18:53 by upinthesky
Really enjoyed this rule set!
on 21. February 2026, 16:58 by Gizmo
I thoroughly enjoyed that puzzle. A new combination of rules for me. Took a little for everything to click, but once you figured it out, the rest was a quick solve.
on 21. February 2026, 15:12 by Ol-Jay
Wow. Very cool, very fun!
on 21. February 2026, 00:00 by Jasperrr
Very fun, took me embarrassingly to figure out the disjoint set also counted for box position. After that, it went pretty smooth.
on 20. February 2026, 17:31 by superkinkel
Very nice idea. An excellent puzzle (albeit I somehow subconsciously read knight instead of rook and quickly ran into trouble ... but finally realized my misreading).
on 19. February 2026, 22:40 by HeyItsErin
Really great puzzle, I had a lot of fun unpacking the rule set and watching everything come together was brilliant.
on 19. February 2026, 22:32 by firespire
Had to look up what "check by a rook" meant as not a chess player. It's a move in chess in a horizontal and vertical motion any number of steps, so you need to ensure it doesn't see the "King" in cross "+" move in the same box.
You say have fun and this is textbook my idea of having fun. Rules new to me and an easy level to solve. You somehow even know I struggle with memory of a 9 digit solution code, I usually have to try and remember two sequences of 4 digits and work out the last missing number when I have got over here.
