Glory of the Liberation of Undermine Raider in Patch 11.1 rewards the Junkmaestro’s Magnetomech Skyriding mount.
The meta-achievement requires players to earn an achievement on every boss encounter in the new Patch 11.1 raid. Since Liberation of the Undermine contains 8 bosses, you will need to earn 8 achievements for the mount.
The mount’s flavor text: “Well-suited for compacting trash into rollable balls. Junkmaestro apocrypha claims these might become worlds of their own if only they could get big enough.”
Here’s what the mount looks like in the game:
