You have an amount of ({R} magic symbol) available equal to three minus the number of +1/+1 counters on Runaway Steam-Kin.
Steps
If Runaway Steam-Kin has three or more +1/+1 counters on it, activate Runaway Steam-Kin by removing three +1/+1 counters from it, adding ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) .
Cast Ignot Chewer for its evoke cost by paying ({R} magic symbol) .
Runaway Steam-Kin triggers, putting a +1/+1 counter on it.
When Ingot Chewer enters the battlefield, it triggers twice.
Resolve the first trigger, destroying target artifact.
Resolve the second trigger, causing you to sacrifice Ingot Chewer.
When Ingot Chewer dies, Pitiless Plunderer and Rakdos trigger.
Resolve the Pitiless Plunderer trigger, creating a Treasure token.
Holding priority, activate the Treasure by tapping and sacrificing it, adding ({B} magic symbol) .
Activate Haunted Crossroads by paying ({B} magic symbol) , putting Ingot Chewer from your graveyard onto the top of your library.
Resolve the Rakdos trigger from step 7, causing you to exile the top five cards of your library, including Ingot Chewer, with the ability to play those cards until end of turn.
If Runaway Steam-Kin has three or more +1/+1 counters on it, activate Runaway Steam-Kin by removing three +1/+1 counters from it, adding ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) .
Cast Ingot Chewer from exile for its evoke cost by paying ({R} magic symbol) .
Repeat from step 3.
Results
Infinite LTB.
Infinite ETB.
Infinite sacrifice triggers.
Infinite death triggers.
Infinite storm count.
Exile your library with the ability to play the exiled cards until your next turn.