Maddening Melody. While the knight is conscious, it plays music audible out to 90ft. All hostile creatures that can hear this music and start their turn within 30ft of the knight must succeed on a DC 11 Wisdom saving throw or take 4(2d4) psychic damage.

Anti-magic Susceptibility. The knight is incapacitated while in the area of an anti-magic field. If targeted by dispel magic, the knight must succeed on a Constitution saving throw against the caster's spell save DC or fall unconscious for 1 minute.

Kickdown. The knight deals double damage to constructs and doors. It can also cast Thaumaturgy and Knock at will, using Charisma as its spellcasting ability.

Multiattack. The knight can make two bash attacks with its accordion.

Bash. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (1d8+ 3) bludgeoning damage. 

Armor Cage. The knight targets one humanoid of Medium size or smaller. The target must succeed a DC 13 Strength saving throw or become grappled by the knight as they are encased in the suit of armor. While grappled in this way the target is also restrained and has disadvantage on its saving throw against the knight's Maddening Melody ability.