Arthur

Arthur is a Jester-themed miniboss with 75 HP, 5 damage, 4 movement, and 10 Luck, found in Chapter 1 across all three acts (The Alley, The Desert, and The Lab). He only appears after the player unlocks the Jester's collar by completing The Rift. Arthur's entire combat identity revolves around a single ability: Metronome, which casts a completely random spell from the game's pool each turn. This unpredictability is the central challenge, as there is no consistent way to predict or prepare for what he will do next.

Because Metronome selects randomly, Arthur can cast anything from a harmless buff to a devastating area attack in a single turn. The wiki notes that certain extremely powerful spells like Split the Atom are excluded from his pool, preventing instant party wipes, but the remaining options still include potent offensive and utility spells that can swing the fight dramatically. Arthur also has a basic melee attack dealing 5 physical damage that he uses occasionally between Metronome casts. His high Luck stat of 10 further amplifies the variance, making critical hits and ability procs more likely.

There is no true optimal strategy against Arthur since his actions are fully random. The best approach is to bring a versatile party that can handle multiple threat types and focus on dealing damage quickly to end the fight before Metronome rolls something catastrophic. Save-scumming is a viable option: changing equipped items on your cats between attempts alters the random number seed, which changes which spells Metronome selects. Arthur has both Champion and Robo variants with enhanced stats. His name is possibly a reference to Arthur Fleck from the 2019 film Joker, and his smile has been noted to resemble the Trollface internet meme.