Get a Garchompite Z Stone in Pokemon Legends Z-A Via Mystery Gift

Go go go! Claim yourself a Mystery Gift in Pokemon Legends Z-A now and you can unlock the ability to obtain a Garchompite Z stone to evolve your Garchomp into Mega Garchomp Z by defeating Mega Garchomp Z in a battle.

This requires that you have completed one or more hyperspace adventures in the Mega Dimension DLC to encounter the Mega Garchomp Z Pokemon. You can use Mystery Gift under "Link Play" menu option after you have unlocked the Rewards feature in Mable's Research and then by connecting to the internet, this will unlock the battle encounter. One redemption per save file.