Cast Vadrok for its mutate cost by paying ({1} magic symbol) ({WU} magic symbol) ({R} magic symbol) ({R} magic symbol) , merging it under Peregrine Drake.
The Peregrine Drake mutated creature's ability from Vadrok triggers, casting Heat Shimmer from your graveyard without paying its mana cost.
Resolve Heat Shimmer, creating a token copy of the Peregrine Drake mutated creature with haste.
The token copy of the Peregrine Drake mutated creature triggers, untapping five lands you control.
Cast Snap by paying ({1} magic symbol) ({U} magic symbol) , returning the nontoken Peregrine Drake and Vadrok from the battlefield to your hand and untapping two lands you control.
Cast Vadrok for its mutate cost by paying ({1} magic symbol) ({WU} magic symbol) ({R} magic symbol) ({R} magic symbol) , merging it under the token Peregrine Drake mutated creature.
The token Peregrine Drake mutated creature triggers once for each of its Vadrok abilities.
Resolve one of these triggers, casting Heat Shimmer from your graveyard without paying its mana cost.
Resolve Heat Shimmer, creating a token copy of the Peregrine Drake mutated creature with haste.
The token copy of the Peregrine Drake mutated creature triggers, untapping five lands you control.
Resolve a second trigger from step 7, casting Snap from your graveyard without paying its mana cost, targeting the mutated creature that includes the nontoken Vadrok.
Resolve Snap, returning Vadrok from the battlefield to your hand as well as multiple token creatures which cease to exist, and untapping two lands you control.
Resolve any remaining triggers from step 7, casting any noncreature cards with mana value 3 or less that were not already cast since step 7 from your graveyard without paying their casting costs.
Repeat from step 6, adding one additional token Vadrok to each new iteration of the Peregrine Drake mutated creature token.
Results
Infinite casts of all noncreature cards with mana value 3 or less in your graveyard.