piano scale
D♭ natural minor
The major scale started from its sixth degree: same seven notes, a different centre of gravity.
The same sounds spelled from the other side are C♯ natural minor.
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
What is true of it
D♭ natural minor is D♭, E♭, F♭, G♭, A♭, B♭♭ and C♭, and back to D♭.
Its steps are W – H – W – W – H – W – W, where W is a whole step and H a half.
Written correctly it needs 8 alterations, B♭♭ 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.
On the same tonic, D♭ harmonic minor differs from it by exactly one note.
It cannot be written as a key signature at all, because a signature has no room for a double accidental.
Chords made only of these notes
Found by testing every chord in the catalogue against these 7 sounds, not chosen.