Activate Goblin Bombardment by sacrificing Eternal Witness.
When Eternal Witness dies, Mortuary triggers, putting Eternal Witness on top of your library from your graveyard.
Resolve the Goblin Bombardment ability, dealing 1 damage to any target.
Cast Hit the Mother Lode by paying ({4} magic symbol) ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) , exiling Eternal Witness from the top of your library and casting it without paying its mana cost, and creating seven tapped Treasure artifact tokens.
When Eternal Witness and the Treasures enter the battlefield, Amulet of Vigor triggers seven times and Eternal Witness triggers once.
Resolve all Amulet of Vigor triggers, untapping the Treasures.
Resolve the Eternal Witness trigger, returning Hit the Mother Lode from your graveyard to your hand.