Activate a creature by tapping it, adding at least {U}.
Activate Harmonized Trio by tapping it and two other creatures you control, causing it to become prepared.
Cast a copy of Brainstorm by paying {U}.
Murmuring Mystic triggers, creating a creature token.
When the creature token enters, Intruder Alarm triggers, untapping all creatures.
Resolve Brainstorm, causing you to draw three cards and put two cards from your hand onto the top of your library.
Repeat.

Infinite card draw

Infinite draw triggers

Near-infinite creature ETB

Near-infinite creature tokens

Near-infinite magecraft triggers

Near-infinite storm count

Near-infinite untap of all creatures

Intruder Alarm

Harmonized Trio // Brainstorm

Murmuring Mystic

Activate The Tenth Doctor by paying {7}, removing all time counters from Arc Blade.
Arc Blade triggers, causing you to cast it from exile without paying its mana cost.
Murmuring Mystic triggers, creating a creature token.
When the creature token enters, Mana Echoes triggers, adding {C} for each creature you control that shares a creature type with the token.
Resolve Arc Blade.
Repeat.

Infinite creature ETB

Infinite colorless mana

Infinite creature tokens

Infinite damage

Infinite magecraft triggers

The Tenth Doctor

Mana Echoes

Arc Blade

Activate Spellbinding Soprano's encore ability by paying {3}{R} and exiling it from your graveyard, creating a token copy of it with haste for each opponent you have.
Declare each Spellbinding Soprano token as an attacker.
Each Spellbinding Soprano token triggers, causing instant and sorcery spells you cast this turn to cost {1} less to cast for each Spellbinding Soprano token.
Cast Sprout Swarm with buyback by tapping a green creature and any other creature you control.
Murmuring Mystic's first ability triggers, creating a 1/1 Bird Illusion creature token.
Resolve Sprout Swarm, creating a 1/1 Saproling creature token and returning Sprout Swarm to your hand.
Repeat from step 4.

Infinite storm count

Infinite tapped creature tokens

Spellbinding Soprano

Sprout Swarm

Cast Searing Touch with buyback by paying {R}. Electro, Blood Funnel and Murmuring Mystic trigger.
Resolve the Electro trigger, adding {R}.
Resolve the Murmuring Mystic trigger, creating a creature token.
Resolve the Blood Funnel trigger, causing you to sacrifice the creature token.
Resolve the Searing Touch spell.
Repeat.

Combos with "Murmuring Mystic"