Corrosion Zombie

Undead Fortitude. If damage reduces the zombie to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead.

Siege Monster. The Corrosion Zombie deals double damage to structures.

Corrosive Shell. A creature that touches the zombie or hits it with a melee attack while within 5ft of it take 7 (2d6) acid damage. Any nonmagical weapon made of metal or wood that hits the zombie corrodes. After dealing with damage, the weapon takes a permanent and cumulative -1 penalty to damage rolls. If its penalty drops to -5, the weapon is destroyed. Nonmagical ammunition made of metal or wood that hits the zombie is destroyed after dealing with damage.

Death Burst. When the Corrosion Zombie dies it explodes outward releasing its corrosive dust in a 20ft radius. All non-undead creatures within the radius must make a Dex save (DC 15), taking 8d6 acid on a failed save and are subject to its Corrosive Shell ability on a failed save damaging armor instead, taking half damage and are not subject to its Corrosive Shell ability on a successful save.

Multiattack. The Corrosion Zombie can make 2 slam attacks, or 2 Bile Spit attacks.

Slam. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) bludgeoning damage plus 14 (4d6) acid damage. In addition, nonmagical armor worn by the target is partly dissolved and takes a permanent and cumulative -1 penalty to the AC it offers. The Armor is destroyed if the penalty reduces its AC to 10.

Bile Spit. Ranged Weapon Attack: +5 to hit reach 20/50ft., one target. Hit: 20 (5d6+3) poison damage