1. Head to the Solar Station: After defeating all the planets, head to the Solar Station, located in the center of the Astro Knights world.
2. Enter the Time Portal: Once at the Solar Station, enter the Time Portal, which is a large swirling vortex of colors.
3. Travel to the Past: The Time Portal will transport you back in time to the planet X, which you visited earlier in the game.
4. Defeat Time Keeper: On the planet X, you will encounter Time Keeper, the main antagonist of Astro Knights. Defeat Time Keeper in a final battle to save the universe.
5. Return to the Present: After defeating Time Keeper, you will be transported back to the present, where you will be greeted by your allies and celebrated as a hero.
6. Complete the Quest: Finally, you can complete the Astro Knights quest by talking to the NPC named Commander Stargazer, located at the Solar Station. He will reward you with an Astro Knights medallion and congratulate you on saving the universe.