Cast Eternity Vessel by paying {6}. It will enter with a number of charge counters on it equal to your life total.
Cause Eternity Vessel to leave the battlefield. When it does, Donatello triggers, putting a number of charge counters on Darksteel Reactor equal to the number Eternity Vessel had on it.
Darksteel Reactor triggers, causing you to win the game.

Win the game

Eternity Vessel

Darksteel Reactor

Donatello, Mutant Mechanic

Cast Eternity Vessel by paying {6}. It will enter with a number of charge counters on it equal to your life total.
Cause Eternity Vessel to leave the battlefield. When it does, Donatello triggers, putting a number of charge counters on Magistrate's Scepter equal to the number Eternity Vessel had on it.
Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, causing you to take an extra turn after this one.
Repeat step 3 as able each turn.

Lock

Near-infinite turns

Magistrate's Scepter

Animate Solar Array, if needed.
Cast Freed from the Real by paying its mana cost, attaching it to Solar Array.
Activate Solar Array by tapping it, adding {U} and causing the next artifact spell you cast this turn to have sunburst.
Activate Freed from the Real by paying {U}, untapping Solar Array.
Repeat from step 3 as desired.
Cast any artifact spell, triggering its sunburst ability an infinite number of times, either putting infinite +1/+1 counters on charge counters on the artifact.

Infinite +1/+1 counters on a creature

Infinite +1/+1 counters on artifact creatures you cast

Infinite charge counters on artifacts you cast

Solar Array

Freed from the Real

Animate Everflowing Chalice using Donatello.
Activate Everflowing Chalice by tapping it, adding at least {C}{C}{C}
Activate Voltaic Construct by paying {2}, untapping Everflowing Chalice.
Repeat from step 2.

Infinite colorless mana

Infinite untap of artifact creatures you control

Voltaic Construct

Everflowing Chalice

Cause Basalt Monolith to become a creature using Donatello.
Activate Basalt Monolith's first ability by tapping it, adding {C}{C}{C}.
Activate Basalt Monolith's last ability by paying {2}, untapping it.
Repeat from step 2.

Basalt Monolith

Training Grounds

Animate Maskwood using Donatello.
Activate any number of mana-producing creatures you control by tapping them, adding at least {3}.
Activate Maskwood Nexus by paying {3} and tapping it, creating a 2/2 Shapeshifter creature token.
When the Shapeshifter enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Repeat from step 2.
If creatures you control can tap to produce at least {4}, this combo nets infinite mana.

Infinite creature ETB

Infinite creature tokens

Infinite mana creatures you control can produce

Infinite untap of creatures

Intruder Alarm

Maskwood Nexus

Animate Brass Infiniscope.
Activate Brass Infiniscope by tapping it, adding {C}{C} and creating a delayed triggered ability.
Activate Voltaic Construct by paying {2}, untapping Brass Infiniscope.
Repeat steps 2 and 3 as desired.
Cast the spell with {X} in its mana cost, with {X} being at least 2 if you wish to gain life.
Each instance of Brass Infiniscope's delayed triggered ability triggers, causing you to draw a card and gain half X life, rounded down, for each trigger.

Infinite card draw

Infinite draw triggers

Near-infinite lifegain

Near-infinite lifegain triggers

Spell with {X} in Mana Cost

Brass Infiniscope

Animate Spawning Pit using Donatello
Activate Spawning Pit's second ability by removing two charge counters from it due to Blossoming Tortoise, creating a 2/2 Spawn artifact creature token.
Activate Spawning Pit's first ability by sacrificing the Spawn, putting two charge counters on it.
Repeat from step 2.

Infinite creature LTB

Infinite death triggers

Infinite creature sacrifice triggers

Ashaya, Soul of the Wild

Blossoming Tortoise

Spawning Pit

Doc Samson, Super Psychiatrist

Animate Spawning Pit using Donatello.
Activate Spawning Pit's second ability by removing two charge counters from it, creating two creature tokens.
Activate Spawning Pit's first ability twice by sacrificing the creature tokens, putting two charge counters on it.
Repeat from step 2.

Quina, Qu Gourmet

Activate Phyrexian Devourer by paying {0}, exling the top card of your library and putting a number of +1/+1 counters on Phyrexian Devourer equal to that card's mana value.
If Phyrexian Devourer's power becomes seven or greater this way, it triggers.
Holding priority, repeat from step 1 until you have an empty library.
Resolve the first Phyrexian Devourer trigger, causing you to sacrifice it.
When Phyrexian Devourer leaves the battlefield, Donatello triggers, putting a number of +1/+1 counters onto Hallar equal to the number Phyrexian Devourer had.
Cast any kicker or multikicker spell with kicker by paying its mana cost plus its kicker cost.
Hallar triggers, putting a +1/+1 counter on itself, then dealing damage equal to the number of +1/+1 counters on it to each opponent.

Exile your library

Near-infinite +1/+1 counters on a creature

Near-infinite damage

Spell with Kicker or Multikicker

Hallar, the Firefletcher

Phyrexian Devourer

Animate Hourglass of the Lost using Donatello.
Activate Hourglass of the Lost's first ability by tapping it, adding {W} and putting a time counter on it.
Kate's first ability triggers, creating a 1/1 Soldier creature token.
When the Soldier enters, Intruder Alarm triggers, untapping all creatures.
Repeat from step 2.

Infinite white mana

Infinitely large creatures you control until end of turn

Kate Stewart

Hourglass of the Lost

Combos with "Donatello, Mutant Mechanic"