Legendary Pokemon
With all eight badges collected, you now have the ability to battle with - and perhaps catch a legendary Pokemon. In "SoulSilver," this Pokemon is called Lugia and you can find it in the Whirl Islands. To engage in this battle, you must have gone to Ecruteak City and battled the Kimono Girls previously and received the Tidal Bell. You can try to capture Lugia when fighting it, but if you kill it, you cannot find it again to try to capture it.
Victory Road
Victory Road is the path that leads you to the Pokemon League. This road has several wild Pokemon to battle with, but no trainers, so use this opportunity to level up your Pokemon as much as you can for the final five battles in the game's story. The path contains many healing and revival potions, so collect those as you find them. Also, you can backtrack and exit the area and go to the nearest town to heal if your Pokemon lose too much health.
Rival Battle
As you near the exit of Victory Road, you will run into your rival, with whom you have competed throughout the game. Your rival wants one more battle with you to prove he's better once and for all. He explains that he's the one who defeated all of the trainers on Victory Road and that you're next. When you approach him, you will automatically be thrown into battle. However, like previous battles with your rival, this one will not be too difficult.
The Pokemon League
On the Indigo Plateau, you'll find a city where the Pokemon League building resides. This building is home to four elite trainers and the Pokemon League champion, all of whom you must defeat to win the game. The city has a Pokemon Center where you can heal your Pokemon before the battles as well as a Poke Mart where you can stock up on heals and potions. However, you must defeat all five trainers in succession without returning to the Pokemon Center to be declared the new Pokemon League champion.