Junker Heights

Junker Heights comes into play tapped.
{t}Add a {r} or {g} to your mana pool.
{2}Sacrifice Junker Heights and another artifact,
put a mech from your graveyard onto the battlefield.

"Some teenagers found it first. They had no idea
they had been lighting their campfires directly on
the LRM magazine. We're all lucky the surface
plating held up."