Narakasura the demon was killed by SriKrishna on Aasweeja bahula Chaturdasi(around Oct/Nov) as per Hindu Almanac and Hindu mythology. The next day Amavaasya(New moon) is celebrated as Deepaavali by Hindus. Desires, anger, greediness, pride, jealousy, delusion, lethargy, complacency, postponing kriyayoga meditation etc are the negative forces and demonic qualities. These negative forces will not allow the sadhak to do Kriya yoga sadhana.
Moolaadhara, Swadhistana and Manipura are called samsaara/worldly chakras. The negative forces shall confine the sadhak to worldly affairs.
Moolaadhara chakra represents Prithvee tatwa. Prithvee tatwa represents Gandha tatwa. Narakasura is the leader of negative forces in the sadhak. He is the son of Bhoodevi, Soil Goddess. That is Narakasura the Gandha tatwa is the son of Prithvee tatwa.
Gandha tatwa shall confine the consciousness of sadhak to Physical pleasures. This will make the Kundalinee to remain in sleeping state. Sleeping Kundalinee cannot get Godhood.
The sadhak seeks the help of Kootastha Sri Krishna or Sri Krishna Consciousness. Kootastha is the place between eyebrows. Kootastha is the abode of Sri Krishna or Sri Krishna Consciousness. That means the sadhak does intensive dhyana/meditation in Agnachakra/Kootastha. Then the Sri Krishna or Sri Krishna Consciousness shall awaken the Kundalinee nearer to Mooladhara chakra before. The awakened Kundalinee that reached Mooladhara chakra shall illuminate that Mooladhara chakra to glow with its natural effulgence. Such Mooladhara chakra or Bhoodevi shall kill its son Narakasura that is Gandha tatwa which is confined to physical pleasure(s). This will help the Kriyayoga sadhak to further awaken the kundalinee so as to make upper chakras to illuminate with their respective natural effulgences which are so far marred due to sleeping Kundalinee.
This awakening of Kundalinee that is reaching Mooladhara chakra to further his progress in Kriya yoga Sadhana is called NARAKASURA VADHA or killing of the leader of negative forces.The awakened kundalinee that has reached Mooladhara chakra and make the four petals of that chakra to shine with its natural effulgent yellow colour is akin to removing darkness that is massive during Amavasya or New moon is called Deepavali.