https://www.gamespot.com/articles/how-hearthstones-new-boomsday-project-keyword-was-/1100-6460680/

Hearthstone's next expansion, The Boomsday Project, brings Mechs back to the forefront for the first time since the tribe was introduced in Goblins vs Gnomes. A big part of the refreshed Mech focus is the new Magnetic ability, which allows you to stick Mechs together to build your own bot. Lead designer Mike Donais shared some design insights and gave a hat-tip to a classic giant robot in the process.

"We wanted to do something different for Mech, something we hadn't done before," Donais told GameSpot. "And we really liked the idea of you assembling some kind of Voltron-type deal where you're stacking Mechs on top of each other to make the ultimate Mech."