There are a few ways to get a Darkrai in other games:
* Event Distribution: Darkrai was often distributed through events in various Pokémon games. If you have a game with an event code for Darkrai, you can use that to get one.
* Trading: You can trade for a Darkrai from someone who has one. Many online communities and forums facilitate trades between Pokémon players.
* Hacking: While not recommended, you can hack a Darkrai into your game. However, this is against the spirit of the game and could potentially lead to issues with online play.
If you are looking to add Darkrai to your SoulSilver game, your best bet is to find someone who has a spare to trade with.