Death Match + Dockside Extortionist + Brain Freeze + Underworld Breach

Banned

How it works

If Dockside Extortionist and/or Brain Freeze are in your graveyard, you have an additional three cards in your graveyard for each one.
Opponents control at least five artifacts and/or enchantments.

If Dockside Extortionist is in your hand, cast it by paying .
Otherwise, cast it from your graveyard for its escape cost by paying and exiling any three cards from your graveyard except Brain Freeze.
Dockside Extortionist enters the battlefield, triggering itself and Death Match.
Resolve the Dockside Extortionist trigger, creating at least five Treasure tokens.
Resolve the Death Match trigger, giving Dockside Extortionist -3/-3 until end of turn.
Dockside Extortionist dies as a state-based action due to having zero or less toughness.
Activate four Treasure tokens by tapping and sacrificing them, adding .
If Brain Freeze is in your hand, cast it by paying .
Otherwise, cast it from your graveyard for its escape cost by paying and exiling any three cards from your graveyard except Dockside Extortionist.
Brain Freeze's storm ability triggers, creating a copy of Brain Freeze for each other spell you've cast this turn.
Resolve the first two Brain Freezes, causing you to mill six cards.
Resolve all remaining Brain Freezes, causing target player to mill three cards for each Brain Freeze.
Repeat.

In which brackets is this combo allowed, per Spellbook's Banned tier?

1–2 · Exhibition & Core

Spellbook classifies this as Banned — not for these brackets.

3 · Upgraded

Spellbook classifies this as Banned — not for these brackets.

4–5 · Optimized & cEDH

Spellbook classifies this as Banned — not for these brackets.

How it works

If Dockside Extortionist and/or Brain Freeze are in your graveyard, you have an additional three cards in your graveyard for each one.
Opponents control at least five artifacts and/or enchantments.

If Dockside Extortionist is in your hand, cast it by paying .
Otherwise, cast it from your graveyard for its escape cost by paying and exiling any three cards from your graveyard except Brain Freeze.
Dockside Extortionist enters the battlefield, triggering itself and Death Match.
Resolve the Dockside Extortionist trigger, creating at least five Treasure tokens.
Resolve the Death Match trigger, giving Dockside Extortionist -3/-3 until end of turn.
Dockside Extortionist dies as a state-based action due to having zero or less toughness.
Activate four Treasure tokens by tapping and sacrificing them, adding .
If Brain Freeze is in your hand, cast it by paying .
Otherwise, cast it from your graveyard for its escape cost by paying and exiling any three cards from your graveyard except Dockside Extortionist.
Brain Freeze's storm ability triggers, creating a copy of Brain Freeze for each other spell you've cast this turn.
Resolve the first two Brain Freezes, causing you to mill six cards.
Resolve all remaining Brain Freezes, causing target player to mill three cards for each Brain Freeze.
Repeat.

Commander brackets

In which brackets is this combo allowed, per Spellbook's Banned tier?

1–2 · Exhibition & Core

Spellbook classifies this as Banned — not for these brackets.

3 · Upgraded

Spellbook classifies this as Banned — not for these brackets.

4–5 · Optimized & cEDH

Spellbook classifies this as Banned — not for these brackets.