Legendary Killer Sudoku is for the most skilled solvers only. Rated 10.0 and above, these grids have no given digits and no easy cages: progress comes from long deductions that combine cage sums, uniqueness arguments and contradiction chains across the whole board. Expect hours, not minutes.
Legendary killer puzzles are rare by nature — most cage layouts simply do not produce this much difficulty — so the supply is small and every entry is verified to have a single solution. For the classic equivalent, see legendary classic Sudoku.