In Unova's Survival Crisis!, when Ash's Pikachu freed Meloetta and sent the Team Rocket members flying with a powered-up Electro Ball caused by excess energy he absorbed from Thundurus earlier, Giovanni was struck by a beam of light from the Reveal Glass, causing him to become overwhelmed by its power and send the Legendary Pokémon on a rampage to destroy the region instead. Giovanni was eventually released from its possession when Jessie, James, and Meowth pushed him out of the spell circle he had been standing in. Following Team Rocket's subsequent retreat, Ridley used the Reveal Glass and Meloetta's song to calm down the rampaging Legendary Pokémon. Afterwards, the Reveal Glass was sealed away once again.
The Reveal Glass made its first proper appearance in Colress Machine, where it was shown to be in Colress's possession, using it to transform Thundurus and Landorus into their Therian Formes to fight Blake.
In The Final Battle, Keldeo broke the Reveal Glass while trying to strike down Colress, causing the forces of nature to revert to their Incarnate Formes and allowing the Swords of Justice to defeat them.
Trivia
The Reveal Glass possesses the colors of the three forces of nature: the left side is blue for Thundurus, the right side is green for Tornadus, and the upper side is orange for Landorus.
In Pokémon Legends: Arceus, with the addition of Enamorus, it's revealed that the Reveal Glass used to have a handle, which is pink like Enamorus.
In Generation V, the Reveal Glass will only work after the player has transferred Landorus from Pokémon Dream Radar. However, since doing this is required to obtain the Reveal Glass in the first place, this behaviour can only be witnessed via cheating.
Origin
The Reveal Glass may be based on the Demon Detecting Mirror, an item in Chinese mythology that could reflect the true identity of a yaoguai. Its design is based on the colors of Tornadus, Thundurus, and Landorus, with the Legends: Arceus design adding the colors of Enamorus.
