The trouble with the term “karma” is it’s been so badly abused by people using it to control others and keep power. What those people say it means, isn’t what it really is,
You can pretty much see the root of karma in the Hermetic maxim, “Like attracts like.”
Or, you get back what yo put in.
Or, what goes around comes around.
When you set up your energy to be a certain way, you will attract more of that to you. If you fear a given outcome you make it more likely to happen. If you harm others that energy stays in your field like a scar and attracts the same energy of harm to you.
So what is “you”?
If you reincarnate and maintain a chain relating your current lie back to your other incarnations, these energy scars can stay with you in layers of your energy being. They are not in the physical or qi body - those are shed and it’s all cleared out. They are in the memories of the astral and emotional layers.
This is also why “repentance” works - but only if it’s internally genuine to you - nobody else can take these scars away you have to reject everything about that energy and not maintain it, even vowing to make amends which directly counteracts and helps dissolve these energetic knots. There’s no such thing as a “sin eater” that can wishful-think away the physics of your energy bodies.
Sadly, these energy blocks do not have to exist for shitty things to happen to people. It isn’t anyone’s fault. We live on a hostile planet and other beings, humans, other animals, energy beings are all also in survival mode and hostile. Most are very stupid and unselfaware. You will go mad trying to justify and make sense of things that have no basis in logic or sanity. So don’t do that to yourself.
Look at the Gnostics who if they hadn’t been all massacred by the Catholic church would have all died ot anyway as they decided this is a prison planet for archons to harvest negative emotions - their explanation for the bs we deal with - and having kids here would be irresponsible. But they were missing the full story, imo, so this was insane. But the Gnostic info is a good place to start. Mystics before and after them agree on this point though, including Robert Monroe of the Munroe Institute - but he took it further into the solution. Which is… enlightenment, i.e., self empowerment to opt out of the energy harvesting.
Here is a good “cliff notes” version of the way Monroe explained it - watch to the end at there’s no short-attention-span TL;DR and the positive stuff that tells you how to beat the system is at the end, and won’t make sense unless you watch the rest to get the foundational model.
My TL;DR - we call these “parasites” generally on BALG forums, and there are many kinds, not just “archons” - as above so below, beings end up becoming like the things that abuse them - see human self-styled “vampires” and “dark trial” types for different kinds of extreme human parasitism, all borne of heavy damage to the human, sometimes over many lifetimes.
The contention of the Gnostics and related is that reincarnation is not about “learning lessons”, that’s a trap and a lie of the archons because they NEED YOUR COMPLIANCE - you have free will, after all.
You have to have good spiritual hygiene and keep your energy “high vibrational” to not feed parasites or attract more. They can’t even see you if you radiate unconditional love. if you radiate anything of pain, misery, fear, we know they will see you as a mark and make you hurt more to make you a better source, and make you hurt others so they produce more as well. They get fat on pain.
You don’t have to play that game, you can be here and still have serenity. Which doesn’t feed parasites.
To do this, you need to KNOW YOURSELF - become enlightened - know why you are how you are and heal all scars, (shadow work) learn to soul travel and plan your way off Earth instead of reincarnating to feed the system, and more importantly, continue your spiritual journey instead of stagnating on Earth and similarly parasitized planets.
This is why we have tutorials emphasizing how basic and important spiritual hygiene is for every mage - Unofficial Tutorials: Spiritual Hygiene & Defense Basics Collection.
This in itself is allowing you to feed the parasites. They LOVE your confusion and discomfort, it keeps them alive.
So you are right to instinctively want to find ways to get rid of it. 
Allowing and stepping back from negativity helps, observe it but don’t see it as part of you, don’t try to control it or resist it, it’s only an energy flowing through you that is not yours.
Understand why you need to know, instead of just accepting every emotion you have as valid - you are hardwired by survival needs of the animal you incarnate into to abhor uncertainty. The conscious mind is designed to identify things in milliseconds to limit danger and instantly react. We are the descendents of survivors, not people who went "is that bear, I wonder..?. arrgh".
So you are following the amygdala, the most primitive of the 3 brains we have, which for esoteric purposes that isn’t helpful. It’s why we make up role playing ideas because we so uncomfortable with uncertainty and we need to feel strong. You have to get over being the hunted animal and let things be, until in good time you find the way intuitively, rather than interrupting intuition with fake certainty.