False Appearance The corrosion crawler pupa is indistinguishable from a normal stalactite or stalagmite.
Corrosive Burst. When the corrosion crawler pupa dies, every creature within 5 feet of it must make a DC 11 Dexterity saving throw or take 9 (4d6) acid damage. In addition, nonmagical armor worn by a creature that fails the save 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. Also, any nonmagical weapon within this area that is unattended or carried by a creature that fails its save corrodes, taking a permanent and cumulative −1 penalty to damage rolls. If its penalty drops to −5, the weapon is destroyed.
Nonmagical ammunition that hits the corrosion crawler pupa is destroyed after dealing damage.
Hatch. When a corrosion crawler pupa dies roll a d6. On a 5 or 6 it attempts to hatch a corrosion crawler if it has not done so already. The corrosion crawler must make a DC 11 Constitution check or it dies.
Hatch. When a creature would provoke an attack of opportunity roll a d6. On a 1-4 the pupa may not attempt to Hatch for the next 24 hrs. On a 5 or 6 the corrosion crawler inside attempts to hatch. The corrosion crawler must succeed on a DC 11 Strength check. On a success the corrosion crawler pupa dies with a Corrosive Burst and the corrosion crawler is hatched into the space previously occupied by the pupa.