There are many types of dark nights in a spiritual context, and I am only experienced with a couple.
There is the dark night of the senses, where identification with the body and as a human being is loosened.
And there is the dark night of the soul, where remaining identifications are triggered, wear out, and softened or fall away.
For me, the dark night of the senses lasted for about a year. When I was fifteen, I drank a large amount of alcohol for the first and last time, and the day after, January 1st, I felt the world becoming more (and eventually very) distant. I even remember the exact situation and moment it happened. This lasted for a year, and I thought something was seriously wrong and went to see several doctors and specialists, and had several neurological tests done. Not surprisingly, in hindsight, they didn’t find anything. Now, I see that I could call it an “absorption into the witness”. It was still very dualistic, but a very simple dualism between “I” here witnessing, and the world (including my body, emotions, thoughts) “out there” quite distant from me, and appearing quite unreal, like a dream, as if I could put my hand right through it. This seemed to be triggered by the alcohol, and I had been an atheist for several years by that time. This dark night of the senses, if that’s what it was, didn’t seem “spiritual” at all to me. Prior to this, I had some years where I felt very much an outsider and awkward socially, and also “frozen” in some ways. That too may be seen as part of this dark night, or at least leading up to it. (I sometimes hear “dark night” being referred to as “dry” and losing interest in the world. I wonder if this is not another form of a dark night of the senses.)
About one year later, when I was sixteen, I walked down a gravel road from my parent’s house (where I still lived) and the mail box. It was winter, a dark evening, with a very clear starry sky, and a big wind going through it. I walked down the road, and suddenly God awoke to itself as all there is. Nothing was left out, and nothing as not God (or consciousness, or love, or awakeness, or alive). Consciousness revealed itself to itself as all there is, beyond and embracing all polarities. This led to a sense of huge downloads of information and insights, especially during sleep (I haven’t encountered anything significant in any teachings that wasn’t clear to me back then, apart from more culture-bound terminology and specific practices). There was also a sense of huge energies running through my body, as if high levels of electricity ran through ordinary housing wiring. Everything revealed itself as light and consciousness, and I started seeing energies and auras (of everything and everyone), and became hyper sensitive to energies in myself and other people. I also had a huge amount of inspiration running through me for making music and art, and writing. Amazing synchronicities were abundant. There was a sense of “everything” falling into place, and metaphorically being held in God’s hand. I also had huge amounts of energies and was extremely productive in terms of studies, work, art, writing, and spiritual practice (tai chi, chi gong, meditation, prayer). This lasted for several years, although started very gradually diminishing after about five years or so. (Especially when I moved into a Zen center, ironically enough!) I now recognize this as a quite typical opening and kundalini awakening (awakening of the kundalini energy), but at the time, I had no context for it. It took many years before I found someone who could relate, and I also found some books written by people who something similar had happened to. (The first one was Meister Eckhart, then later people like Yogananda, St. Francis, Jesus, and some historical Buddhist teachers.)
After about ten years, what I now recognize as a dark night of the soul started. It was very gradual at first, initiated by me not following my guidance and moving to a place I didn’t feel was the right for me (because of a relationship). Then, about five years in, I got back into meditation and also received diksha. This led to a laser like focus and clarity, which shifted into a very simple and clear non-dual awakening (there was clearly no “I” to be found anywhere). After about six months, it again shifted, and this time into a much more intense phase of the dark night of the soul. I got chronic fatigue, lied in a dark room for weeks and months, and was unable to function much. At the same time, huge amounts of shadow material surfaced. In the beginning, this was a very archetypal and ancestral material. (For instance, I had a night where innumerable “evil” and dark figures from many cultures and prehistoric cultures paraded in front of me, and for each one, I briefly became it, as if I took on the “mask” of that figure.) Then, after a couple of years, much more personal material – wounds and trauma – from this life surfaced, and this was actually much more challenging. I also had about six months of immense and primal dread and terror, where I hardly slept at all, and couldn’t function apart from walking for hours in deep despair in the woods near where I lived. (Just prior to this, I asked to be shown what’s left….! A reminder to be careful about those “dangerous” prayers.) This more intense phase of the dark night of the soul has lasted for more than five years now, and it’s been a phase where “everything” has fallen apart in my life including health, ability to work, relationships, my home, old friendships and much more. Whenever something encouraging seems to happen, that too often falls apart one way or another, and often in ways that seem outside of my control. (Although partly triggered by me being caught up in what’s surfacing in me and acting “out of character”.) It’s very much the reverse of the ten years following the initial opening and awakening. It’s as if my life and world has been turned inside-out and upside-down, and not in the way I expected or wanted. (Although I knew, from the beginning of the initial awakening, that I would have to go through a dark night phase of my life to help ground and mature.)
My sense is that the initial awakening was of the head center (a clear seeing of all as God), followed by the heart center (all as love). During this time, I knew the process would deepen somehow, and be more deeply, fully and richly “embodied”. The following and current dark night of the soul seems to be much more about the belly center, a felt sense of all as God (and healing and cleaning out old wounds and trauma, and primal fear and clutching). I also assume that the chronic fatigue partly has to do with the intensity of my process in my teens and twenties, and partly – or mainly – has to do with me “living a lie” and not following my guidance in certain areas of my life (relationship related).
Note: The initial opening followed by a kundalini awakening brought with it many of the typical side effects, including seeing auras, hypersensitivity to energies in myself and others, download of information and artistic inspiration, electric things (in my case, especially light bulbs) burning out in periods of high intensity, a sense of very high intensity energies running through my system (which didn’t feel prepared for it or really capable of handling that much, although it did), food intolerances (quite severe, at times), synchronicities, and much more. Similarly, the dark night of the soul mirror, in my case, many of the typical characteristics of a dark night of the soul, including inner and outer structures falling apart, loss of all kinds, old friendships falling away (often not from my choice), illness (chronic fatigue), a period of immense and primal dread and terror, fear of the future, old wounds and trauma surfacing, unfelt emotions and unmet impulses and drives surfacing, sometimes acting “out of character”, odd and intensely uncomfortable (unless I meet it as sensations) sensations in the body, and much more.