What is Feasible in the Light?
Inside we are capable of being awake, thinking, living and growing. Life runs different systems and the different systems run support for complex living. Inside you will find the immune system which outgrows its enemies, the organ system which holds and pads wiring, skin and bones that cover and provide structure, neural system to send and get data, the glandular system to grow adult parts and chemistry, and a diverse spine system to provide enough fire to live.
Outside there is daylight, sunshine, rain and air. At ground level there land and water - land from swamp to desert to volcano, and water bodies from lakes to oceans. Green plants fill the landscape and provide much of the sustenance. Separately, we go outside to know what is going on, to get to places, and to socialize.
What is Feasible in the Darkness?
What do you need to live? What do you do, or need, to be healthy? What is the level of happiness that don't want to part with? The darkness won't get far if you want to live. Otherwise, you will vascillate between control of others and minimal control of yourself. You will wish others to death because you are an immature life, and you will be very close to death as well.
You may promote evil, but you have to maintain life nonetheless. You have to maintain your life somewhere, either inside or outside. Something has to go right to support the things that go wrong. Evil itself doesn't do more than it has to. It conserves fuel to live.
If you live damned, either you pay for your consequences or you have someone else pay for them. Either way someone has to pay for the consequences and evolve in the process. If you live, created out of your consequences, you have no consequences when it is awful and no consequences when it is great. You stay immature.
In general evil is feasible, but after time and inundation, people vote against evil, so that it doesn't overtake them or their options. Evil is ultimate destruction, so everything evil will die, and new life will then restart, or all things will reincarnate to start over on a better standing.