The portal is on an asteroid in the asteroid belt at X-11 Y-82 and it is sealed by the Golden Key. The only way to open it is to pull out the Key. To do so, you must defeat all three of the planets (jungle, fire, ice) and have all three of the Space Knights with you on the planetoid.
You have to push it open.
Presumably he is still stuck in his castle in the far galaxy, and no longer has the Orb or the Golden Key to open the portal again. If you return to the asteroid, it is just a dead end.
After you beat all three planets (fire, ice, jungle) and have all three Space Knights with you, you can go to the secret planetoid at X-11 Y-64 in the asteroid belt. Pull the Golden Key from the crystal to open the portal.
It is at X-11 Y-84 in the Asteroid Belt. You can only go there after you have defeated all three of the planets (Jungle, Fire, and Ice) and have all three Space Knights with you, so that you can open the portal behind the Golden Key.
it is open ing June 10 or you can buy a ticket for 500 credits
There is no 4th space knight. You are the fourth knight, the Chosen One who will rescue the princess. When you have beaten the three planets, and have all three knights with you, go to the Giant Asteroid at X-11 Y-84 and you can pull the Golden Key to open the portal there.
you have to finish the puzzle then click on the door
Move the Mill to open the window
The knights will tell you of a secret asteroid hidden in the Asteroid Belt. Go there, and you will find it near X-11 Y-84. You will need all three knights to pull out the Golden Key and open the portal to the castle in a distant galaxy. You will fight the Binary Bard (Mordred) in his robot warrior suit. (see related question)
Once you defeat all three planets (jungle, fire, ice) and have all three knights with you, travel to the Giant Asteroid in the Asteroid Belt (X-11 Y-84) and use the Golden Key to open the portal to Mordred's hideout. (see related question)
Jump across the four Phoenix Eggs from the rope on the left. Key : jump when the egg is OPEN...by the time you land, it is closed.
Back Gate to the Dungeon CellThe front entrance to the dungeon cell does not open. Throwing the switch opens the rear gate, which is accessed from Mordred's secret laboratory.The Golden Key and the Portal GateYou need all three knights with you to pull the Golden Key from the Crystal. This means beating all three planets.(see related questions)