C♯ Locrian — 7th chords
Four-note stacks of thirds on each degree — root, 3rd, 5th, 7th. The added 7th gives jazz, gospel, and modern classical voicings their distinctive colour.
All 7 seventh chords in sequence
Degree 1 · i°7C#m7b5
Degree 2 · IImaj7Dmaj7
Degree 3 · iii7Em7
Degree 4 · iv7F#m7
Degree 5 · Vmaj7Gmaj7
Degree 6 · VI7A7
Degree 7 · vii7Bm7