Cast Time Warp by paying {3}{U}{U}, getting an extra turn after this one.
Play Mystic Sanctuary to put Time Warp on top of your library.
Cast Capsize for its buyback cost by paying {4}{U}{U}, returning Mystic Sanctuary to your hand.
Move to your next turn.
Repeat.

Infinite turns

Skip your draw step

Mystic Sanctuary

Capsize

Time Warp

Cast Temporal Manipulation by paying {3}{U}{U}, getting an extra turn after this one.
Play Mystic Sanctuary to put Temporal Manipulation on top of your library.
Cast Capsize for its buyback cost by paying {4}{U}{U}, returning Mystic Sanctuary to your hand.
Move to your next turn.
Repeat.

Temporal Manipulation

Cast Walk the Aeons by paying {4}{U}{U}, getting an extra turn after this one.
Play Mystic Sanctuary to put Walk the Aeons on top of your library.
Cast Capsize for its buyback cost by paying {4}{U}{U}, returning Mystic Sanctuary to your hand.
Move to your next turn.
Repeat.

Walk the Aeons

Cast Capture of Jingzhou by paying {3}{U}{U}, getting an extra turn after this one.
Play Mystic Sanctuary to put Capture of Jingzhou on top of your library.
Cast Capsize for its buyback cost by paying {4}{U}{U}, returning Mystic Sanctuary to your hand.
Move to your next turn.
Repeat.

Capture of Jingzhou

Activate Gilded Lotus by tapping it, adding {U}{U}{U}.
Cast Capsize with buyback by paying {U}{U}, returning Gilded Lotus and Capsize to your hand.
Cast Gilded Lotus by paying at most {1}.
Repeat.
If your opponents have drawn five or more cards this turn, this combo will net infinite colored mana.

Infinite colored mana

Infinite magecraft triggers

Infinite storm count

Heliod, the Radiant Dawn // Heliod, the Warped Eclipse

Gilded Lotus

Float at least {15}{U}{U}.
Cast Doubling Cube by paying {2}.
Activate Doubling Cube by paying {3} and tapping it, doubling the amount of mana in your mana pool. This will result in you adding at least {10}{U}{U}.
Cast Capsize with buyback by paying {4}{U}{U}, returning Doubling Cube and Capsize to your hand.
Repeat from step 2.

Infinite blue mana

Infinite mana permanents you control can produce

Return any number of permanents to their owner's hand during each of your turns

Doubling Cube

Deal combat damage using Medomai, triggering its ability, causing you to take an extra turn after this one.
During your extra turn, cast Darksteel Mutation by paying {1}{U}, attaching it to Medomai.
Declare Medomai as an attacker, as it does not have its restriction due to Darksteel Mutation.
Holding priority, cast Capsize with buyback by paying {4}{U}{U}, returning Darksteel Mutation and Capsize to your hand.
Repeat from step 1.

Medomai the Ageless

Darksteel Mutation

Cast Capsize paying for buyback targeting Ugin's Nexus.
Orvar triggers, creating a token copy of Ugin's Nexus.
The token copy of Ugin's Nexus is put into the graveyard due to the legend rule.
The Ugin's Nexus copy triggers, exiling itself and you take an extra turn after this one.
Resolve Capsize returning itself and Ugin's Nexus to your hand.
Pass the turn.
Cast Ugin's Nexus.
Repeat.

Orvar, the All-Form

Ugin's Nexus

Deal combat damage using Medomai, triggering its ability, causing you to take an extra turn after this one.
During your extra turn, cast Witness Protection by paying {U}, attaching it to Medomai.
Declare Medomai as an attacker, as it does not have its restriction due to Witness Protection.
Holding priority, cast Capsize with buyback by paying {4}{U}{U}, returning Witness Protection and Capsize to your hand.
Repeat from step 1.

Witness Protection

Activate Scroll of Fate by tapping it, manifesting Wormfang Manta from your hand.
Pay {5}{U}{U} to turn Wormfang Manta face up.
Cast Capsize with buyback by paying {4}{U}{U}, returning Wormfang Manta from the battlefield to your hand and putting Capsize back into your hand.
Wormfang Manta's LTB ability triggers, creating an extra turn after this one.
Repeat each turn.

Wormfang Manta

Scroll of Fate

Deal combat damage using Medomai, triggering its ability, causing you to take an extra turn after this one.
During your extra turn, cast Amphibian Downpour by paying {2}{U}, attaching it to Medomai.
Declare Medomai as an attacker, as it does not have its restriction due to Amphibian Downpour.
Holding priority, cast Capsize with buyback by paying {4}{U}{U}, returning Amphibian Downpour and Capsize to your hand.
Repeat from step 1.

Amphibian Downpour

Deal combat damage using Medomai, triggering its ability, causing you to take an extra turn after this one.
During your extra turn, cast Dress Down by paying {1}{U}. When it enters the battlefield, it triggers, causing you to draw a card.
Declare Medomai as an attacker, as it does not have its restriction due to Dress Down.
Holding priority, cast Capsize with buyback by paying {4}{U}{U}, returning Dress Down and Capsize to your hand.
Repeat from step 1.

Dress Down

Deal combat damage using Medomai, triggering its ability, causing you to take an extra turn after this one.
During your extra turn, cast Humility by paying {2}{W}{W}.
Declare Medomai as an attacker, as it does not have its restriction due to Humility.
Holding priority, cast Capsize with buyback by paying {4}{U}{U}, returning Humility and Capsize to your hand.
Repeat from step 1.

Humility

Activate Nardole by tapping it, adding at least six {U} that can only be spent to cast noncreature spells.
Cast Capsize with buyback by paying {4}{U}{U}.
Chakram Retriever triggers, untapping Nardole.
Resolve Capsize, returning target permanent to its owner's hand and returning Capsize to your hand.
Repeat.
You may also repeat this loop during each of your turns.

Nardole, Resourceful Cyborg

Chakram Retriever

Activate Vault of Catlacan's second ability by tapping it, adding six {U}.
Wild Growth triggers, adding {G}.
Activate Voyaging Satyr by tapping it, untapping Vault of Catlacan.
Activate Instill Energy by paying {0}, untapping Voyaging Satyr.
Cast Capsize with buyback by paying {4}{U}{U}, returning Instill Energy from the battlefield to your hand, and then returning Capsize to your hand.
Cast Instill Energy by paying {G}, attaching it to Voyaging Satyr.
Repeat.
If you control seven or more artifacts, this combo nets infinite colored mana.

Storm the Vault // Vault of Catlacan

Voyaging Satyr

Wild Growth

Instill Energy

Activate Vault of Catlacan's second ability by tapping it, adding six {U}.
Wild Growth triggers, adding {G}.
Activate Voyaging Satyr by tapping it, untapping Vault of Catlacan.
Activate Nature's Chosen's first ability by paying {0}, untapping Voyaging Satyr.
Cast Capsize with buyback by paying {4}{U}{U}, returning Nature's Chosen from the battlefield to your hand, and then returning Capsize to your hand.
Cast Nature's Chosen by paying {G}, attaching it to Voyaging Satyr.
Repeat.
If you control seven or more artifacts, this combo nets infinite colored mana.

Nature's Chosen

Activate Relic of Sauron's first ability by tapping it, adding {U}{U}.
Cast Capsize with buyback by paying {U}{U}, returning Relic of Sauron and Capsize to your hand.
Cast Relic of Sauron by paying {0}.
Repeat.

Combos with "Capsize"