If held by a Darkrai, the Darkranite allows it to Mega Evolve into Mega Darkrai if its Trainer has a Key Stone. A Trainer can only have one Mega-Evolved Pokémon at any given moment.
Prior to the release of Mega Dimension, an internal file of Pokémon Legends: Z-A referred to the IDs of a nonexistent Darkranite, along with the Heatranite and Zeraorite, indicating they were originally implemented in the base game but were cut.
In addition, their internal item IDs are not grouped with the other Mega Stones introduced in Mega Dimension, instead being where they would be if they were introduced in the base game of Pokémon Legends: Z-A; in the Darkranite's case, it is between the Heatranite and Emboarite.
