piano scale
C♯ whole tone
C♯1D♯2E♯3F𝄪♯4G𝄪♯5A𝄪♯6
Six notes, every step a whole one. There are only two of these scales in all, and every note can be heard as the tonic.
The same sounds spelled from the other side are D♭ whole tone.
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
C♯WD♯WE♯WF𝄪WG𝄪WA𝄪WC♯
What is true of it
C♯ whole tone is C♯, D♯, E♯, F𝄪, G𝄪 and A𝄪, and back to C♯.
Its steps are W – W – W – W – W – W, where W is a whole step and H a half.
Written correctly it needs 9 alterations, F𝄪, G𝄪 and A𝄪 among them. That is what the letters force, and it is also why nobody writes music in this key: the same notes spelled from the other side are easier to read.
Chords made only of these notes
Found by testing every chord in the catalogue against these 6 sounds, not chosen.