5-cell killer cage summing to 18

3 digit sets sum to 18 across 5 cells. Without other constraints this cage is loose; the value comes from pairing it with the cage's row, column, or box context — every digit ruled out elsewhere narrows which combinations remain.

Locked digits: 1, 2. Whichever combination is in play, these digits sit somewhere inside the cage — meaning the cage's shared row, column, and box can't have any of them anywhere outside the cage.

Forbidden digits: 9. This digit never appears in this cage no matter which combination resolves; you can eliminate it from every cell of the cage as you pencil in candidates.