Grand Abyss is a room located on the upper level of Sanctuary Fortress in Metroid Prime 2: Echoes. It is significant because it's the only way to access Vault, which contains Screw Attack, an essential item for completing the game. The room consists of a large open space that separates both sides, bridged only by two maintenance drones that appear in the middle when the room is first loaded. While the only intended way to cross this room normally is with Screw Attack, there are multiple methods to do so that don't require Screw Attack. Additionally, this is the room in which Vault Skip can be performed, which is the fastest method of getting Screw Attack.
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Crossing Grand Abyss Without Screw Attack
Boost Jump method
The fastest and best method of crossing Grand Abyss involves using a Boost Jump. Once outside, you can use the walls on both sides to perform the Boost Jump. (Right Wall side is better as it doesn't make you move while in Morph Ball) The window for getting the Instant Unmorph is fairly lenient in this area, so it's mostly a matter of timing your inputs correctly.
It it worth noting that it is possible to fail the jump, but still make it to the other side after touching the Terminal Fall trigger. This happens if you touch an invisible trigger that updates where the game will place you before touching the terminal fall trigger. Due to the long loading time of Vault, this doesn't lose any time, so there is no penalty for touching the terminal fall trigger as long as it places you on the other side afterwards and you're fast enough to reach the door.
Extended Dash method
This is inferior to the Boost Jump method due to needing to scan lock on one of the distant maintenance drones, but it still allows for multiple attempts. By performing an Extended Dash off of one of the drones, you will get enough speed to cross the gap. Again, it's possible to fail the jump and still make it as long as you make it far enough to touch the fall respawn trigger.
Scan Dash method
This is the oldest method of crossing Grand Abyss, reliant upon the maintenance drones in the middle of the room as well as one used in the distance as a scan point. This is the most precise and most difficult method of crossing Grand Abyss as well as being one of the traditional run killers in the past as this was the only way to cross the room. This method can also be done only once per playthrough, as once you activate the trigger that causes the drones to start moving, the room's layer will change permanently and the drones will never be in their original positions ever again.
TODO: Complete explanation and Add Details
Vault Skip is the absolute fastest way to get into Vault. Like the name suggests, you can completely skip the Vault puzzle and get Screw Attack immediately by letting the room load around you when you're inside the chamber where it is located. To do this:
- Position yourself on the second Maintenance Drone in Grand Abyss with either a Boost Jump or with a Scan Dash and wait for the perfect moment to Dash to another Maintentance Drone in the air (specifically one of the distant ones). These Maintenance Drones have a special property, which is once they reach a certain point in the room, they teleport to their "initial spawn point" and by being on top of it, it teleport with you as well.
- Once you're about to get teleported, you're required to look in a specific angle where Vault's door scan lock will be, so you can Dash into the Aether at the perfect moment.
- After that, there is a specific part of the world background where you need to line your crosshair with and walk forwards to get to Screw Attack.
- Because the room loads faster than you can get into it, it is required to perform several Pause Delay Buffers to make the room load slower, they range between 6 to 11.