Here's why:
* Battle Revolution is a separate game from the main Pokemon series games: It focuses on battling and does not have the usual features of catching Pokemon in the wild, breeding, or finding them in specific locations.
* Legendaries are primarily obtained through specific events, trades, or by completing certain challenges in the main games: Battle Revolution does not have these features.
The only way to get legendary Pokemon in Battle Revolution is by:
* Trading them from a DS game: You can transfer Pokemon from your DS games to Battle Revolution, including legendary Pokemon you've obtained in the main games.
* Using the online features: Battle Revolution had online features that allowed players to trade and battle with each other. This was a way to obtain legendary Pokemon from other players.
However, the online features of Battle Revolution are no longer functional since the online servers were shut down in 2014.
Therefore, unless you have access to a DS game and a way to transfer Pokemon to Battle Revolution, you will not be able to get legendary Pokemon in this game.