Dark forces can range from negative thoughts that compound and rearrange the way matter forms, to negative emotions being projected onto others, to the effects that come from absent of light beings that are parasitic in nature (feeding off of a host to survive).

The variety and range here is extensive, and the most important thing to know is that there is balance and light is infinitely more powerful than that that is without it. 

To understand the depth and complexity of the dark force world we have to first understand that in order to exist within this Universe you must be composed of light, and this light comes from our connection to Source/God. When a being is absent of light it must then take/gather light in order to exist and operate. Now, what is important to understand here is the spectrum that exists within the dark force world so to elaborate I thought I’d break it down into a few questions. 

1. Are all dark forces evil? No. They are not. In fact a large portion of absent of light beings and situations are either completely void of emotion and ill intent OR they are unintentional and a byproduct of unconscious energetic projections. 
2. What about those that could be classified as evil? First, let’s expand our awareness & perception of what is happening here. Which can be best summarized by a desire for more power and control. When beings make the choice to go the ‘Dark Force” route they fall under the classification of absent of light because the only way to do this is to sever all relation and connection to God/Source. This is a byproduct of not wanting to go down the path that is aligned with Light and the Highest good of all and for all. AKA: they want what they want when they want it, how they want it. And when it comes to how that impacts us, they will manipulate, abuse, control, and severely impact all light beings to the benefit of themselves. 
3. What is considered a Dark Force? Simply put, if it is negatively impacting matter around and within us it is likely absent of light. Whether that is negative emotions and thoughts that we absorb from other people, rituals (dark absent of light intentions that are created to interfere with our life in various ways) , parasitic beings (think demons), or simply something like a ghost that is separated from Spirit. Whatever it is, if it is a a force, being, or a product of those two that is void of/ separate from Source/God it qualifies as Dark Forces. Again the spectrum mentioned in question 1 is always relevant.