Activate Phyrexian Altar by sacrificing Ardent Elementalist, adding .
When Ardent Elementalist dies, Mortuary triggers, putting Ardent Elementalist on top of your library from your graveyard.
Cast Hit the Mother Lode by paying 4, exiling Ardent Elementalist from the top of your library and casting it without paying its mana cost, and creating six tapped Treasure artifact tokens.
When Ardent Elementalist and the Treasures enter the battlefield, Amulet of Vigor triggers six times and Ardent Elementalist triggers once.
Resolve all Amulet of Vigor triggers, untapping the Treasures.
Resolve the Ardent Elementalist trigger, returning Hit the Mother Lode from your graveyard to your hand.
Activate six Treasures by tapping and sacrificing them, adding 4.
Repeat.
This loop is a masterclass in recycling, turning the high mana value of Hit the Mother Lode into an engine for infinite mana and spell-casting. When you cast Hit the Mother Lode, its discover mechanic effortlessly snags Ardent Elementalist off the top of your library—since the spell's mana value of 7 is less than 10—while simultaneously flooding the board with six tapped Treasure tokens. Thanks to Amulet of Vigor, those Treasures instantly untap upon entry, ready to be sacrificed alongside Phyrexian Altar to feed the loop and recoup your red mana. Meanwhile, Mortuary ensures that whenever Ardent Elementalist is sacrificed to Phyrexian Altar, it goes right back to the top of your library to be discovered all over again, while Ardent Elementalist's own trigger continuously plucks Hit the Mother Lode back out of your graveyard to hand.