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Three rows, three columns, total elimination.
Swordfish extends the X-Wing idea from two rows to three. If a candidate appears in exactly three rows, and every one of its possible cells across those rows falls inside the same three columns, the candidate can be eliminated from the rest of those columns.
Not every row needs all three candidate cells filled. Some rows may only have two of the three columns represented, as long as no candidate cell falls outside the trio of columns.
This is an expert-level technique, so the demo grid below is seeded at the expert difficulty. Take your time scanning row by row.