I have a 12th house Venus in cancer currently being transmitted by the new moon and the sun who has mercury and mars combust around him right now, similar to my mars/sun/mercury stellium in H1. So, of course I have to stay up and write this instead of going to sleep! This Venus placement has, as a lot of other people have noted, led me to pursue and find myself in pretty much exclusively extremely intense romantic relationships that take me to extreme heights of spiritual bliss and unconditional cosmic love...that (more often then not) does not last, and usually devastates my life, leading to rebuilding.
I have been married once and it was such an abusive and toxic relationship we were not legal for a week before I became victim to felony battery. Our engagement happened 10m into our first real meeting - like every other serious relationship I have been in it happened pretty much overnight - I am not kidding when I say I have never once "dated" anyone - it has been either all in or single. I do not think this placement has much opportunity for lasting, mundane, "love relation." I have read of these "secret affairs" but I have always been loyal & honest with my partners so who is having James Bond style clandestine torrid trysts, it ain't me...maybe I should seriously reconsider my relationship style
but, now that I think of it, most of my partners in the past did seem to want to keep me secret- not calling me girlfriend even though we lived together, never saying "I love you" even after 2.5 years & diamonds, calling me "secret wife," introducing me by saying "we have been hanging out since..." (that last one I had already had a marriage ceremony with!)...etc. Makes sense- if my 12hVenus were in Aries or Scorpio I would probably not be at the brunt of this.
But honestly, this venus makes me not be even remotely interested in sexuality unless I am emotionally enmeshed with the person, even if only in my own world. I have gotten so used to this, and even furthered by my yogic and spiritual practices, I often go long periods celibate - sometimes loving it, sometimes yearning for a suitable lover. And to be honest I have tended to go for people that are mean, neglectful, manipulative, or abusive in some way. That super sensitive cancer in this placement has definitely resulted in unintentional (and intentional) masochism. She is also opposite Neptune in Cap in H5. I still after years feel as though I do not really understand where my ex-partners stand in regard to whether they are or ever have really been trustworthy in regard to keeping my heart safe. As I move forward and think more deeply about this Venus placement I feel as though it is an extreme challenge to find secure, lasting, and fulfilling love. The desire, and a very deep yearning one at that as Venus has seen and felt it all by this point and is nostaligic for the most glorious of knowledges and enthralling of loves, sometimes so badly one is willing to put up with almost any risk to "go there" with someone who can match the energy and passion of the native.
I practice Kundalini yoga (not devotedly, but peripherally) & have worked as a professional Dominatrix. 12H Venus is weird. Sex, love, energy, magic, healing - it is all the same for me. And, I can COMPLETELY shut off my libido for long periods. I do not ever need sex, but man when I get going I am an insatiable nymphomaniac. It has mystified & exhausted many who I have shared that intimacy with.
As I enter into my 2nd Saturn cycle I think a new approach to this Venus is in order: it seems to be best expressed with self-love and spiritual love for all, for the pure love of the heart&spirit. Soul expression. Someone said it is a placement for writers - I am a published poet & screenwriter & blogger with an international audience. It seems the more high-art&fine-beauty attributes of Venus have a positive manifestation here whereas the more base Eros type of attributes go a bit "off the deep end" unless somehow kept in check by intense spiriutal discipline.