Master Killer Sudoku starts empty and gives nothing away. Rated 7.0–9.9, these puzzles need chains of cage combinations that span several boxes, repeated use of the 45 rule on overlapping regions, and notes you trust completely. One wrong candidate can hide the next step for a long time.
This level is for solvers who already finish expert grids and want the arithmetic to bite harder. Every puzzle has exactly one solution and your board is saved after every move, so a master grid can span several sessions. Want the same rating without cages? Try master classic Sudoku.