Firn, Pillager Foundry

{t}: Add {r}{r} to your mana pool, spend this mana only to cast instants, and Firn deals 2 damage to you.
{4}{r}{t}: Destroy target robot and Assemble a Contraption.
When there are five or more robots in an opponent's graveyard Assemble all Contraptions. When Firn is destroyed you lose 7 life.