Excal-heim
Immutable Form. The creature is immune to any spell or effect that would alter its form.
Magic Resistance. The creature has advantage on saving throws against spells and other magical effects.
Morbid Construction. The creature has advantage on saving throws against being charmed or intimidated, and magic can't put it to sleep.
Drops: Chain Sword
Multiattack. The creature makes two attacks.
Chain Sword. Melee Weapon Attack: +7 to hit, reach 5 ft, one target. Hit: 13 2d8+4 slashing damage.
Double damage to structures. Upon dealing 20 damage, target gains 1 level of exhaustion.
Blast Wave. The creature fires a chest-mounted cannon at the ground, targeting all creatures within a 40-foot-cone.
Each target must make a DC 15 STR save, taking 5 bludgeoning damage and being thrown 10ft(landing prone) on a fail.