piano scale
F♯ Locrian
F♯1G♭2A♭3B4C♭5D♭6E♭7
The only mode of the major scale whose fifth is diminished, which is why its tonic chord cannot rest.
The same sounds spelled from the other side are G♭ Locrian.
Written out
Every accidental is written in, rather than left to a key signature, so the letters can be read one at a time.
The step pattern
F♯HGWAWBHCWDWEWF♯
What is true of it
F♯ Locrian is F♯, G, A, B, C, D and E, and back to F♯.
Its steps are H – W – W – H – W – W – W, where W is a whole step and H a half.
On the same tonic, F♯ Phrygian differs from it by exactly one note.
Chords made only of these notes
CmajorCmaj7major seventhDmajorD7dominant seventhEmminorEm7minor seventhF♯dimdiminishedF♯m7♭5half-diminished seventh
Found by testing every chord in the catalogue against these 7 sounds, not chosen.