Activate Ancient Den by tapping it, adding {W}.
Activate Mind over Matter by discarding Razortide Bridge, untapping Ancient Den.
Activate Ancient Den by tapping it, adding {W}.
Activate Tameshi by paying {W} and returning Ancient Den from the battlefield to your hand, returning Razortide Bridge from your graveyard to the battlefield.
Activate Mind over Matter by discarding Ancient Den, untapping any applicable permanent.
Activate Tameshi by paying {W} and returning Razortide Bridge from the battlefield to your hand, returning Ancient Den from your graveyard to the battlefield.
Repeat.

Infinite landfall triggers

Infinite mana permanents you control can produce

Infinite self-discard triggers

Tameshi, Reality Architect

Mind Over Matter

Ancient Den

Razortide Bridge

Activate Metalworker by tapping it and revealing at least three artifact cards from your hand, adding at least six {C}.
Activate Urza by paying {6}, creating a token copy of Razortide Bridge that is a 1/1 Soldier.
When the Razortide Bridge token enters the battlefield, Retreat to Coralhelm triggers, untapping Metalworker.
Repeat.
If you have four or more artifact cards in hand, this combo nets infinite colorless mana, and you may target any artifact you control to get infinite copies of them.

Infinite colorless mana

Infinite copies of artifacts you control

Infinite creature tokens

Infinite ETB

Infinite creature copies of artifacts you control

Infinite mana creatures you control can produce

Infinite untap of creatures you control

Urza, Prince of Kroog

Metalworker

Retreat to Coralhelm

Activate Prototype Portal by paying {0} and tapping it, creating a token copy of Razortide Bridge.
When Razortide Bridge enters the battlefield, Tiller Engine triggers, untapping it.
Activate the Razortide Bridge token by tapping it, adding {U}.
Activate Filigree Sages by paying {U}, untapping Prototype Portal.
Repeat.

Combos with "Razortide Bridge"