Secret Door

Defender
{4}{U}: Venture into the dungeon. Activate only as a sorcery. (Enter the first room or advance to the next room.)

Shortcut Seeker

Whenever Shortcut Seeker deals combat damage to a player, venture into the dungeon. (Enter the first room or advance to the next room.)

Fall from Favor

Enchant creature
When Fall from Favor enters the battlefield, tap enchanted creature and you become the monarch.
Enchanted creature doesn't untap during its controller's untap step unless that player is the monarch.

Azure Fleet Admiral

When Azure Fleet Admiral enters the battlefield, you become the monarch.
Azure Fleet Admiral can't be blocked by creatures the monarch controls.

Bar the Gate

Counter target creature or planeswalker spell. Venture into the dungeon. (Enter the first room or advance to the next room.)

Dungeon Delver

Commander creatures you own have "Room abilities of dungeons you own trigger an additional time."

Imoen, Mystic Trickster

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
At the beginning of your end step, if you have the initiative, draw a card. Draw another card if you've completed a dungeon.
Choose a Background (You can have a Background as a second commander.)

Canal Courier

When Canal Courier enters the battlefield, you become the monarch.
Whenever Canal Courier and another creature attack different players, Canal Courier can't be blocked this combat.

Aarakocra Sneak

Flying
When Aarakocra Sneak enters the battlefield, you take the initiative.

Trailblazer's Torch

When Trailblazer's Torch enters the battlefield, you take the initiative.
Whenever equipped creature becomes blocked, it deals 2 damage to each creature blocking it.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Staunch Throneguard

Vigilance
When Staunch Throneguard enters the battlefield, you become the monarch.