The first chamber is the only part of Mt. Silver that is dark enough to require the use of Flash. Go right to find an X Accuracy on the southeast platform, then loop around to the left to reach an Escape Rope. On the north end of the next platform is an Ultra Ball. The largest platform opens into a T-intersection to the north; turn left to get a Max Elixir, then go right to reach the opening in the northeast.
Surf out into the lake, climb the waterfall, and enter the small chamber to find a Max Revive. Step out of the lake and go north to climb up a triple stairway. Use Surf again and climb the northeast waterfall to reach another small chamber with a Full Restore. Swim back across the lake and enter the opening to the north.
Cross the land bridge to meet the strongest opponent in the game, former Champion Red. His is the highest-leveled team of any Trainer, ranging from 73 to 81. If you want to stand a chance against him, your Pokémon should have reached at least level 75. Even with a type advantage, Red's Pokémon won't go down without a fight.
Defeated, he pauses for a second in stunned silence. Then in the blink of an eye, Red is gone. A moment later, the credits roll for the second time.
Having scaled Mt. Silver and defeated the legendary Trainer, the only thing left to do is to complete the Pokédex. Pokémon Gold and Silver brought the total number of Pokémon up to 251, so there is plenty of training left to do!