Ishavasya Upanishad (3 )

असुर्या नाम ते लोका अन्धेन तमसाऽऽवृताः ।ताँस्ते प्रेत्याभिगच्छन्ति ये के चात्महनो जनाः ॥३॥

*Verily, those worlds of the asuras are enveloped in blind darkness; and there to they all repair after death who are slayers of Atman *

Here in the third stotra states about the unillumined worlds clouded by the blinding darkness of ignorance.
Slayers of atman means ?
Those who have destroyed their self. Who perform works, without having arrived at a knowledge of the true Self. Upanishad clearly indicates they go after death to those worlds of demons.

In our previous posts we were talking about evolution and karma theory and how noone can exists without action. 

Know that Work is a spiritual longing. It originates in the deepest recesses of being, whether it is a happy or unhappy service. The impulsion to act persists due to the finite existence, again, this finite existence is due to our prarabdha karma . When our body moves in a given direction - we call it work,,The mind moves in a given direction - we call it thought, The feelings move in a given direction-we call it desire. 
All these move towards a wholeness of experience, to become one. Towards brahman.

There are hundreds of explanations available but the gist is
We have to blend *avidya* and *vidya* together for the sake of freedom and immortality, says the Upanishad. 

"The bondage to which we are subjected by action, day in and day out, will make us disgusted with everything, and we will be automatically freed from the impulse to act. The world (maya) itself will liberate us from its clutches when we have paid our debts to it."

Paying our debts and performing action we may transcend our karmic cycle.  It is ignorance of not performing our duties and searching for God sitting somewhere in the sky. And it is utter ignorance to get stuck in our action n worldly desire alone.