The Shining Legends is a surprise new expansion for Pokémon TCG coming right at the heels of Burning Shadows. The set is a special expansion which focuses specifically on Legendary and Mythical Pokémon
Shining Legends is a 73 card expansion based on the Japanese equivalent the "Strength Expansion Pack Shining Legends". The Japanese counterpart was released on July 15, 2017, but the release date for the English set is October 6, 2017.
This set brings with it several neat things. For one, it brings Shining Pokémon back into the TCG. Shining Pokémon haven't been in the game since Neo Revelation. They're based on the Shiny Pokémon within the anime and video game, and have a few special features.
For one, they are extremely rare, and feature different colorations from standard Pokémon. But, perhaps more excitingly, their attacks often use multiple energy types.
An important change to these Shining Pokémon is that they are no longer restricted to 1 per deck.
One of the things to keep in mind when purchasing shining legends is that it's not available in standard booster packs. Instead, you'll need to purchase set related products. These include the Shining Legends Elite Trainer Box, and Shining Legends Pin Collections.
Booster packs within those products contain 11 cards with 2 guaranteed foil cards.
The Shining Legends Trainer box will include ten Shining Legends boosters (so a total of 20 guaranteed foil cards), in addition to the standard items you receive with an elite trainer box.
There's also the Shining Legends Pin Box which features either a foil Pikachu, MewTwo, or Alolan Raichu promo card, collectors pin, and three Shining Legends booster packs. This means you'll get 6 guaranteed foil cards.
Other products may be released, but this is all we know for now.