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Jellyfish

Four-line fish: a digit confined to a 4x4 line pattern. expert

2345682368368467891784689178584578456868468146814584847847836893685678578368357892368923681368245678157823468785835789123828123838682826368136825895828918261818739219256342157946951437744236759
Digit 8 in rows 3/6/7/9 fits only at the marked positions, which line up on columns 1/4/6/9, one per line, so erase it from everywhere else in columns 1/4/6/9. (Shown on a plain grid.)

The four-line fish, rarest of the family: a digit confined to four columns across four rows. The same cover logic as the x-wing and swordfish, one size larger.