In Pokemon Legends: Z-A, players collect Mega Shards, but their purpose is not immediately clear.
The early game serves as a tutorial, introducing Wild Zones, Battle Zones, and Mega Crystals, which contain Mega Energy and can be shattered to obtain Mega Shards.
Mega Crystals are described as collections of Mega Energy.
Author's summary: Mega Shards are collected in Pokemon Legends: Z-A.