According to Osho, the 'unconscious mind' is the dreamlike wave of inherited memories and conditionings that survives body to body, habituated to pain and ruling your life. The 'dark night of the soul' is the turbulent crisis when your innermost being asserts itself and this mind’s mastery breaks, culminating in no-mind and entry into the universal.
It’s like a pile of old habits and dreams steering you, and the darkest time comes when that pile cracks so your real self can take the wheel.