Scan the smallest regions first
A region with only two or three cells has fewer candidates. Cross out any cell on a used row or column, then check diagonal neighbours.
Make every King do more work.
The best solvers do not inspect every square equally. They repeat a short scan that turns each confirmed King into a chain of useful exclusions.
Mark the full row and column
After placing a King, immediately mark every other cell in that row and column. Visible consequences prevent repeated mental work.
Check every royal corner
The diagonal rule is easy to miss. Each King removes the four corner-touching cells even when those cells belong to different realms.
Look for region–line locks
If all candidates for a region lie on the same row, no other region can use that row. The same idea works vertically with columns.
Count what remains, not what is filled
When a row has one unresolved cell after exclusions, that cell is forced. This reverse view is often faster late in a puzzle.
Pause before using a hint
Run the same scan order—small region, row, column, diagonals—one more time. A consistent routine is more valuable than a lucky guess.