• The delight dragon emits an aura that turns all weapons around it into toys, and can turn itself into laughing gas
• The halfling head chef dazzles opponents by throwing spices in their eyes
• The brainchild gains abilities if those observing it believe it has them
• The bibliodaemon, manifestation of death by bureaucracy, slows enemies by pointing out that they don’t have clearance to perform their actions
• Animated tea carts attack by squirting scalding hot tea at you
• The gliminal, manifestations of vital energies, kill you by giving you so much extra HP that you explode
• The yeongno, a traditional Korean monster that eats rich people, beats the crap out of you with your own money
• A mob of corn leshies, nature spirits that animate corn plants, can form into corn mazes to disorient the enemy

Feel free to add your own!