The Crystal Empire

Lots of crystals, tall palace

Kingdom

Ponish

Unknown

Bits

Love

Jousting, Yews vs Dragons (foal game),

Sunny, unless the Crystal Ponies don't feed their love to the Heart

Surrounded by open plains and icy mountains

Common crops

Beyond the Crystal Mountains. Exact location unnamed

Originally inhabited by dragons.
A group of Crystal Keepers came form Portmanteau, drove them out, and stole the crystal heart from a dead dragon to drive away the icy winds that had previously been kept at bay by the original inhabitants.

King Sombra's war
Celestia and Luna fought King Sombra to free the Crystal Ponies. The king was turned into shadow, but the Empire disappeared.

Unknown