Activate Gwenna by tapping it, adding {G}{G} that can only be spent to cast creature spells or to activate abilities of creatures.
Cast Ghalta by paying {G}{G}.
Brinelin and Gwenna trigger.
Resolve the Brinelin trigger, returning Thrasta from the battlefield to your hand.
Resolve the Gwenna trigger, putting a +1/+1 counter on it and untapping it.
Activate Gwenna by tapping it, adding {G}{G} that can only be spent to cast creature spells or to activate abilities of creatures.
Cast Thrasta by paying {G}{G}.
Brinelin and Gwenna trigger.
Resolve the Brinelin trigger, returning Ghalta from the battlefield to your hand.
Resolve the Gwenna trigger, putting a +1/+1 counter on it and untapping it.
Repeat.

Infinite +1/+1 counters on Gwenna

Infinite ETB

Infinite LTB

Infinite storm count

Brinelin, the Moon Kraken

Gwenna, Eyes of Gaea

Ghalta, Primal Hunger

Thrasta, Tempest's Roar

Cast the artifact creature from your hand by paying {0}.
Brinelin triggers, returning Mycosynth Golem from the battlefield to your hand.
Cast Mycosynth Golem by paying {0}.
Brinelin triggers, returning the other artifact creature from the battlefield to your hand.
Repeat.

Mycosynth Golem

Activate Sol Ring by tapping it, adding {C}{C}.
Cast Mana Vault by paying {1}.
Displacer Kitten triggers, blinking Brinelin.
When Brinelin enters the battlefield, it triggers, returning Sol Ring from the battlefield to your hand.
Activate Mana Vault by tapping it, adding {C}{C}{C}.
Cast Sol Ring by paying {1}.
Displacer Kitten triggers, blinking Brinelin.
When Brinelin enters the battlefield, it triggers, returning Mana Vault from the battlefield to your hand.
Repeat.

Infinite colorless mana

Displacer Kitten

Sol Ring

Mana Vault

Cast Invasion of Arcavios by paying {3}{U}{U}.
When Invasion of Arcavios enters the battlefield, it triggers, returning Beacon of Tomorrows from your graveyard to your hand, or searching your library for Beacon of Tomorrows and putting it into your hand, if needed.
Cast Beacon of Tomorrows by paying {6}{U}{U}.
Brinelin triggers, returning Invasion of Arcavios to your hand from the battlefield.
Resolve Beacon of Tomorrows, causing you to take an extra turn after this one and shuffle it into your library.
Repeat each turn.

Infinite turns

Invasion of Arcavios // Invocation of the Founders

Beacon of Tomorrows

Cast Invasion of Arcavios by paying {3}{U}{U}.
When Invasion of Arcavios enters the battlefield, it triggers, returning Walk the Aeons from your graveyard to your hand, or searching your library for Walk the Aeons and putting it into your hand, if needed.
Cast Walk the Aeons by paying {4}{U}{U}.
Brinelin triggers, returning Invasion of Arcavios to your hand from the battlefield.
Resolve Walk the Aeons, causing you to take an extra turn after this one.
Repeat each turn.

Walk the Aeons

Activate Sol Ring by tapping it, adding {C}{C}.
Cast Mox Amber by paying {0}.
Displacer Kitten triggers, blinking Brinelin.
When Brinelin enters the battlefield, it triggers, returning Sol Ring from the battlefield to your hand.
Activate Mox Amber by tapping it, adding one mana of any color among legendary creatures or planeswalkers you control.
Cast Sol Ring by paying {1}.
Displacer Kitten triggers, blinking Brinelin.
When Brinelin enters the battlefield, it triggers, returning Mox Amber from the battlefield to your hand.
Repeat.

Infinite mana of colors among legendary creatures and planeswalkers you control

Mox Amber

Cast Invasion of Arcavios by paying {3}{U}{U}.
When Invasion of Arcavios enters the battlefield, it triggers, returning Nexus of Fate from your graveyard to your hand, or searching your library for Nexus of Fate and putting it into your hand, if needed.
Cast Nexus of Fate by paying {5}{U}{U}.
Brinelin triggers, returning Invasion of Arcavios to your hand from the battlefield.
Resolve Nexus of Fate, causing you to take an extra turn after this one and shuffle it into your library.
Repeat each turn.

Nexus of Fate

Cast Skitterbeam Batallion by paying {9}.
Brinelin triggers, returning the other creature with mana value 9 from the battlefield to your hnad.
When Skitterbeam Batallion enters the battlefield, it triggers, creating two token copies of itself.
Cast the other creature with mana value 9 for its emerge cost by paying {0} and sacrificing a Skitterbeam Batallion token.
Brinelin triggers, returning the nontoken Skitterbeam Batallion from the battlefield to your hand.
Cast Skitterbeam Batallion for its emerge cost by paying {0} and sacrificing a Skitterbeam Batallion token.
Repeat from step 2.

Combos with "Brinelin, the Moon Kraken"