Declare any other creature as an attacker.
Holding priority, activate Brass Squire by tapping it, attaching Dinosaur Headdress to the attacking creature, and causing the creature to become a copy of Medomai the Ageless.
Deal combat damage using the creature.
The creature triggers, causing you to take an extra turn after this one.
Move to your postcombat main phase.
Activate Dinosaur Headdress' equip ability by paying {2}, attaching it to Brass Squire.
Repeat each turn.

Infinite turns

Lock

Medomai the Ageless

Paleontologist's Pick-Axe // Dinosaur Headdress

Brass Squire

Declare Armory Automaton as an attacker.
Armory Automaton triggers, causing you to attach Dinosaur Headdress to it, and causing Armory Automaton to become a copy of Medomai the Ageless.
Deal combat damage using Armory Automaton.
Armory Automaton triggers, causing you to take an extra turn after this one.
Move to your postcombat main phase.
Activate Dinosaur Headdress' equip ability by paying {2}, attaching it to any other creature you control.
Repeat each turn.

Armory Automaton

Declare Balan as an attacker.
Holding priority, activate Balan by paying {1}{W}, attaching Dinosaur Headdress to it and causing Balan to become a copy of Medomai the Ageless.
Deal combat damage using Balan.
Balan triggers, causing you to take an extra turn after this one.
Move to your postcombat main phase.
Activate Dinosaur Headdress' equip ability by paying {2}, attaching it to any other creature you control.
Repeat each turn.

Balan, Wandering Knight

Declare any creature as an attacker.
Holding priority, activate Dinosaur Headdress' equip ability by paying {0} if it's the first equip ability you've activated this turn, or {2} otherwise, attaching it to the attacking creature, and causing the creature to become a copy of Medomai the Ageless.
Deal combat damage using the creature.
The creature triggers, causing you to take an extra turn after this one.
Move to your postcombat main phase.
Activate Dinosaur Headdress' equip ability by paying {2}, attaching it to any other creature you control.
Repeat each turn.

Forge Anew

Declare any other creature as an attacker.
Holding priority, activate Auriok Windwalker by tapping it, attaching Dinosaur Headdress to the attacking creature, and causing the creature to become a copy of Medomai the Ageless.
Deal combat damage using the creature.
The creature triggers, causing you to take an extra turn after this one.
Move to your postcombat main phase.
Activate Dinosaur Headdress' equip ability by paying {2}, attaching it to Auriok Windwalker.
Repeat each turn.

Auriok Windwalker

Declare any creature as an attacker.
Holding priority, activate Dinosaur Headdress' equip ability by paying {2}, attaching it to the attacking creature, and causing the creature to become a copy of Medomai the Ageless.
Deal combat damage using the creature.
The creature triggers, causing you to take an extra turn after this one.
Move to your postcombat main phase.
Activate Dinosaur Headdress' equip ability by paying {2}, attaching it to any other creature you control.
Repeat each turn.

Leonin Shikari

Activate Dinosaur Headdress' equip ability by paying {2}, attaching it to Priest of Gix and causing Priest of Gix to become a copy of Cavalier of Night.
Activate Hammerhead by sacrificing Priest of Gix.
When Priest of Gix dies, its second ability triggers, returning itself from your graveyard to the battlefield.
When Priest of Gix enters the battlefield, it triggers, adding {B}{B}{B}.
Resolve the Hammerhead ability
Repeat.

Combos with "Paleontologist's Pick-Axe // Dinosaur Headdress"