You have a basic Mountain, Forest or Swamp in library.
Steps
Play
Riveteers Overlook.
Riveteers Overlook enters the battlefield, triggering itself and
Stone-Seeder Hierophant.
Resolve the
Stone-Seeder Hierophant trigger, untapping it.
Activate
Stone-Seeder Hierophant by tapping it, untapping any land you control.
Resolve the
Riveteers Overlook trigger, causing you to sacrifice it, then search your library for a basic Forest, Swamp or Mountain card, put it onto the battlefield tapped, and gain 1 life.
The basic land enters the battlefield, triggering
Stone-Seeder Hierophant, untapping
Stone-Seeder Hierophant.
Activate
Stone-Seeder Hierophant by tapping it, untapping
Scaretiller.
Activate
Scaretiller by tapping it, adding ({G} magic symbol) .
Scaretiller triggers, returning
Riveteers Overlook from your graveyard to the battlefield tapped.
Repeat from step 2.
Results
Near-infinite landfall triggers.
Near-infinite lifegain.
Near-infinite lifegain triggers.
Near-infinite mana lands you control can produce.
Put all basic Forests, Mountains, and Swamps from your library onto the battlefield tapped.