Activate Field of Ruin's second ability by paying {2}, tapping and sacrificing it, targeting any nonbasic land an opponent controls.
Holding priority, cast Radiant Performer by paying {3}{R}{R}.
When Radiant Performer enters the battlefield, it triggers, copying Field of Ruin's ability for each other nonbasic land your opponents control.
Resolve the first Field of Ruin ability, destroying the land it it targeting, then causing each player to search their library for a basic land card and put it onto the battlefield.
River Song triggers for each opponent who searches this way.
Resolve the first trigger, putting a +1/+1 counter on it and dealing damage equal to its power to an opponent.
Repeat step 6 for each other trigger.
Repeat from step 4 for each other Field of Ruin ability.

Near-infinite damage

River Song

Radiant Performer

Field of Ruin

Activate Field, targeting a land and triggering Rings of Brighthearth.
Pay to copy the Field effect, targeting a different land.
Resolve both triggers and the resulting Ob Nixilis triggers, forcing all opponent to lose 20 life.
Use Crucible of Worlds to play Field.
Repeat steps 1-3.

Near-infinite lifeloss

Ob Nixilis, Unshackled

Rings of Brighthearth

Crucible of Worlds

Activate Field of Ruin's second ability by paying {2}, tapping and sacrificing it, targeting any nonbasic land an opponent controls.
Holding priority, cast Radiant Performer by paying {3}{R}{R}.
When Radiant Performer enters the battlefield, it triggers, copying Field of Ruin's ability for each other nonbasic land your opponents control.
Resolve the first Field of Ruin ability, destroying the land it it targeting, then causing each player to search their library for a basic land card and put it onto the battlefield.
Ob Nixilis' first ability triggers for each opponent who searches this way, causing each opponent to sacrifice a creature and lose 10 life.
Repeat from step 4 for each other Field of Ruin ability.

Combos with "Field of Ruin"