Darkness on the Horizon

Navigate the treacherous Darkness on the Horizon level in Super Mario Galaxy's Bowser's Dark Matter Plant. Master platforming and defeat Bowser to earn the Grand Star.

This page offers a walkthrough of Darkness on the Horizon found in Bowser’s Dark Matter Plant, which is the Boss level of the Bedroom dome. It requires 33 stars to unlock the galaxy.

In the starting section, you’ll be introduced to a few of the areas that will become more prominent and tricky later in the level. You’ll need to take the moving platforms across the dark matter to the rotating tiles area. Next, cross the rotating platforms over to the gravity sections, where you’ll be reminded of how the gravity walls work by jumping across platforms and keeping an eye on the arrows on the walls that denote the direction of gravity. In the next area, climb up a pole being circled by Goombas, either by defeating them or jumping onto the pole and working your way up.

In the Dark Matter Paths section, a Luma will warn you about holes in the path that will suck you into the dark matter below, instantly costing a life. Avoid these holes by jumping to other platforms and back when it’s safe. Once on solid ground, walk a bit before encountering more paths across dark matter, again watching out for holes and using platforms to reach safety.

In the Gravity Rooms area, stand on platforms in specific places to avoid falling into the Dark Matter. Screenshots in the original guide show where to stand, such as on the top left side of a cross shape when moving into a green gravity section.

In the Free the Lumas area, spin attack crystals to free Lumas, which create stairs to reach the Boss fight. An extra life mushroom can also be freed from a crystal.

The Bowser Boss Fight is similar to the last one in The Fiery Stronghold, with attacks including Fire Balls, Electric waves (requiring jumps over circular electrical waves), and Groundpound. A new attack is the Dark Spin attack, which damages and pushes Mario back. To defeat Bowser, lure him to groundpound on blue domes. This will expose fiery lava that damages Bowser, causing him to run away. You must run in the opposite direction to catch him and spin attack to incapacitate him. He will then spin in his shell; again, run in the opposite direction to catch him and spin him again. Failing to catch him in time requires repeating the process. Upon defeat, Bowser leaves behind a Grand Star.