Activate Martyr's Cause by sacrificing Forsaken Miner, targeting any opponent.
Pitiless Plunderer triggers when Forsaken Miner dies, and Forsaken Miner triggers when you commit the crime in step 1.
Resolve the Pitiless Plunderer trigger, creating a Treasure token.
Activate the Treasure by tapping and sacrificing it, adding {B}.
Resolve the Forsaken Miner trigger, causing you to pay {B} to return it from your graveyard to the battlefield.
Resolve the Martyr's Cause ability from step 1.
Repeat.

Infinite LTB

Infinite ETB

Infinite sacrifice triggers

Infinite death triggers

Forsaken Miner

Pitiless Plunderer

Martyr's Cause

Sacrifice Murderous Redcap to Martyr's Cause to prevent all damage to a creature.
Murderous Redcap's persist triggers, returning it to the battlefield.
Murderous Redcap returns to the battlefield with a +1/+1 counter and a -1/-1 counter which cancel out.
Murderous Redcap triggers, dealing 2 damage to any target.
Repeat.

Infinite damage

Murderous Redcap

Renata, Called to the Hunt

Combos with "Martyr's Cause"