When sex goes from being a physical to a heart based to a spiritual based experience, then the serpent gets raised as Moses raised the serpent on the cross. The snake is transformed much like the carnal flesh will one day be transformed to immortality in the resurrection. Raising the kundalini correctly unlocks spiritual portals and you can receive the keys of discernment, and etc.
When you feel it rise, it makes you laugh and cry all at the same time.
Don't confuse it with yoga and inviting demons in and stuff. It will happen when you learn how to sexually connect on a soul level. For me, I felt it completely physically go from the base of my spine and up to my heart. I am still working on getting it to my brain.
You can imagine your spiritual and creative drive flowing through you and for women it is like they receive phallic energy and fountains out the head. I don't know but that men go in the opposite direction.
In the occult, anal sex is used to raise kundalini to give the ability to have psychic and remote viewing gifts, but they are trapped to use in spirit prison, or the lower part of the spiritual 4d world. They do this to children in rituals and then use their energy bodies to do remote work. This is why black helicopters pick up people's 4d energy at night and use it in spying, space program, and other stuff.
Everything you see in movies about secret intelligence, even Harry Potter is about witchcraft. In the Chamber of Secrets Ginny is Mind controlled by voldemort and caries out ritualistic behavior in a trance. This stuff actually happens.
So, the bad guys use it for evil gain. But it is good, if you engage it in a sacred married experience, you open portals to higher spiritual dimensions. I am not referring to anal sex, as anal sex also causes bondage to the abuser as the abuser becomes the strong man and takes over the mind.
A good book I read from the library to help you get started is called "Don Juan and the art of Sexual Energy". It is shamanic practices taught from Mexican culture.
A good exercise is to find a tree, and lay down and take a nap by the tree. In your dream, strive to communicate or even become the tree.
Another exercise is to dream of something, such as a white stone, and "anchor it" to physical reality by looking for that stone in real life. As you start to find elements of your dreams in waking life, you begin to bridge what is possible with the impossible, Making your dreams a reality.
We are vessels. We can learn to hold our own spirits and the spirit of our beloved so we can become one. That raises the kundalini.
Jesus said anything is possible to him that believeth.
Have you ever listened to music that felt so good your body shivered or got goosebumps? That is a long the lines of a kundalini experience.