34 cards where the text includes “monarch” and the color identity ≤ BRW

Archon of Coronation (New Capenna Commander #192)
Champions of Minas Tirith (Tales of Middle-earth Commander #10)
Court of Ambition (Commander Legends #114)
Court of Ardenvale (Wilds of Eldraine Commander #21)
Court of Embereth (Wilds of Eldraine Commander #24)
Court of Grace (Commander Legends #16)
Court of Ire (Commander Legends #170)
Court of Locthwain (Wilds of Eldraine Commander #23)
Crimson Fleet Commodore (Commander Masters #211)
Crown-Hunter Hireling (Conspiracy: Take the Crown #50)
Crown of Gondor (Tales of Middle-earth Commander #75)
Custodi Lich (New Capenna Commander #244)
Emberwilde Captain (Commander Legends #175)
Éomer, King of Rohan (Tales of Middle-earth Commander #52)
Feast of Succession (Commander Masters #158)
Forth Eorlingas! (Tales of Middle-earth Commander #56)
Garrulous Sycophant (Conspiracy: Take the Crown #43)
Invasion of Fiora // Marchesa, Resolute Monarch (March of the Machine #114)
Invasion of Fiora // Marchesa, Resolute Monarch (March of the Machine #114)
Kavu Monarch (Invasion #149)
Knights of the Black Rose (March of the Machine Commander #332)
Marchesa's Decree (Conspiracy: Take the Crown #44)
Oath of Eorl (Tales of Middle-earth Commander #64)
Palace Jailer (Commander Masters #47)
Palace Sentinels (Commander Masters #48)
Protector of the Crown (Conspiracy: Take the Crown #21)
Queen Marchesa (Outlaws of Thunder Junction Commander #239)
Regal Sliver (Commander Masters #724)
Skyline Despot (Commander Masters #254)
Squee, Dubious Monarch (Dominaria United #146)
Starscream, Power Hungry // Starscream, Seeker Leader (Transformers #5)
Starscream, Power Hungry // Starscream, Seeker Leader (Transformers #5)
Staunch Throneguard (Commander Masters #412)
Thorn of the Black Rose (Commander Masters #190)
Throne of the High City (Murders at Karlov Manor Commander #307)
Throne Warden (Conspiracy: Take the Crown #25)

Though this query has ended, its relics still slumber in New Argive.