The "Scale Wall" is a term used in the game to describe a specific challenge within the game. It refers to a series of obstacles you must overcome to reach the Lake Acuity, which is where you'll find the Legendary Pokémon Uxie, Azelf, and Mesprit.
Here's how you overcome the "Scale Wall" challenge:
1. Beat the Elite Four and become Champion: This is the first requirement.
2. Talk to the old man in Celestic Town: He'll tell you about a legendary event in the past.
3. Travel to the Lake Acuity area: You'll encounter several obstacles, including:
* A giant boulder: You need to use Strength to move it.
* A frozen path: You need to use the Flamethrower move on a nearby torch to melt the ice.
* A pathway blocked by a chain: You need to use Cut to clear the chain.
Once you overcome these obstacles, you can access Lake Acuity and encounter the legendary Pokémon.
The "Scale Wall" itself is not a physical barrier, but the challenges you need to overcome to reach the Lake Acuity are often referred to as the "Scale Wall" challenges.