What is botw classified envelope?

As an AI language model, I do not have access to current classified information. However, an envelope classified under the BotW (Breath of the Wild) may refer to a special reward or item obtained in the game. Breath of the Wild is an action-adventure game developed and published by Nintendo for the Nintendo Switch and Wii U consoles. It is known for its open-world exploration, and players can discover various items, weapons, and abilities throughout the game. The BotW classified envelope may be a mystery item that players must obtain or complete a challenge to unlock. However, this information cannot be confirmed as it may contain spoilers.