Activate Viscera Seer by sacrificing Ancient Adamantoise.
When Ancient Adamantoise dies, it and Nim Deathmantle trigger.
Resolve the Nim Deathmantle trigger, causing you to pay 4 to return Ancient Adamantoise from your graveyard to the battlefield and attach Nim Deathmantle to it.
Resolve the Ancient Adamantoise trigger, creating ten tapped Treasure tokens.
When the Treasures enter, Amulet of Vigor triggers ten times, untapping the Treasures.
Resolve the Viscera Seer ability.
Activate four Treasures by tapping and sacrificing them, adding 4.