Ruler of the Black Flame is the first set to feature Tera Pokémon ex with types that differ from their usual types. Type-shifted Tera Pokémon ex use the same Energy types as their usual type for their attacks, but have differing Weakness and Resistance in accordance with their shifted type. Other cards from this set depict Pokémon Centers in the Paldearegion in the illustrations' backgrounds.
This is also the first expansion since the Sun & Moon Era to feature Baby Pokémon that do not evolve into Stage 1 Pokémon, as it includes Cleffa and Bonsly. These cards have each an attack with no Energy and no retreat cost, like those from the LEGEND Era, although unlike previous cards featuring Baby Pokémon, these have Weakness.
The set's Charizard ex can use its Ability to attach Basic Fire Energy cards from the player's deck upon Evolution, which can be used to strengthen Entei's Blaze Ball attack. Another strategy is to use Town Store to find Pokémon Tool cards to attach to Revavroom ex, which can have up to four attached simultaneously because of its Ability.
Ruler of the Black Flame contains four Pokémon ex, four Tera Pokémon ex, 12 illustration rare Pokémon, six special illustration rare Pokémon and Supporter cards, 12 ultra rare full-art etched Pokémon ex and Supporter cards, and three hyper rare gold etched cards.
Ruler of the Black Flame was released in Japanese on July 28, 2023, followed by localized releases in Traditional Chinese on August 11, 2023, in Korean on August 25, 2023, and in Thai on September 29, 2023. The Indonesian set equivalent, Black Shine, released much later on October 27, 2023.
Cards released in this set are included in the English Obsidian Flames expansion.
