Pitiless Plunderer | Eternal Witness | Mitotic Slime (and two other cards)

Cards

({4} magic symbol) ({B} magic symbol) ({B} magic symbol) ({GW} magic symbol) available.

Cast
Nethroi for its mutate cost by paying ({4} magic symbol) ({GW} magic symbol) ({B} magic symbol) ({B} magic symbol) , putting it on top of a non-Human creature you control.
When
Nethroi enters the battlefield, it triggers.
Holding priority, activate
Thermopod's second ability by sacrificing
Nethroi, adding ({R} magic symbol) .
When
Nethroi dies,
Pitiless Plunderer triggers, creating a Treasure artifact token.
Resolve the
Nethroi trigger from step 2, returning
Eternal Witness and
Mitotic Slime from your graveyard to the battlefield.
When
Eternal Witness enters the battlefield, it triggers, returning
Nethroi from your graveyard to your hand.
Activate
Thermopod's second ability twice by sacrificing
Eternal Witness and
Mitotic Slime, adding ({R} magic symbol) ({R} magic symbol) .
When
Eternal Witness and
Mitotic Slime die,
Pitiless Plunderer triggers twice and
Mitotic Slime triggers once.
Resolve both
Pitiless Plunderer triggers, creating two Treasure artifact tokens.
Resolve the
Mitotic Slime trigger, creating two 2/2 Ooze creature tokens.
Activate
Thermopod's second ability by sacrificing an Ooze, adding ({R} magic symbol) .
When the Ooze dies, it and
Pitiless Plunderer trigger.
Resolve the
Pitiless Plunderer trigger, creating a Treasure artifact token.
Resolve the Ooze trigger, creating two 1/1 Ooze creature tokens.
Activate three Treasures by tapping and sacrificing them, adding ({GW} magic symbol) ({B} magic symbol) ({B} magic symbol) .
Repeat.

This combo has been estimated to be Exhibition (Bracket 1+).