How do I obtain Marshadium Z?

Question

I got a Marshadow in trade, but it didn't come with a z-crystal. How do I get one?

Answer 1

Currently, both Marshadow and its Z-Crystal are unobtainable, so to get it you'll have to hack it in or wait for a Marshadow event.

Source

Answer 2

Most likely you find one when you get your own Marshadow from the mystery gift.

Answer 3

In Sun and Moon, only the Mount Tensei Marshadow, redeemable from October 9, 2017 to February 23, 2018, came with a Marshadium Z.

In Ultra Sun and Ultra Moon, a man at the Tide Song Hotel will give you a Marshadium Z, provided you have a Marshadow in your party. It doesn't need to be the Mount Tensei event.

Marshadium Z (Bulbapedia)