6-cell killer cage summing to 25

4 digit sets sum to 25 across 6 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.