EX Legend Maker introduces the location of Mirage Forest, which is home to many rare Pokémon, including the elusive Mew. In Japan, it was later revealed that the human inhabitants of this area (in Holon) were conducting research and experiments on the activities of Mew, which inadvertently caused the creation of Delta Species Pokémon. This information was absent in the English version of EX Delta Species due to the earlier-than-intended release.
The release of EX Legend Maker was delayed due to translation errors. Because of this, Nintendo released EX Delta Speciesbefore EX Legend Maker, throwing the English sets out of sequence with the Japanese sets again and creating a gap in the string of δ Delta Species Pokémon set releases. Nintendo also did this with EX Deoxys (although purposefully).
The Japanese version of this set included several cards that first debuted in EX Emerald; one of particular interest to Japanese players being the Stadium card Battle Frontier.
The reverse-holographic and holographic cards use the same “cosmic” foil (the type first seen in the Team Rocket expansion set); the reverse-holographics distinguished only by the EX Legend Maker set logo. The reverse-holographic versions of the holographic rares also have foil name text, HP text and rarity symbols.