Bridgebite

Overview
When the bite of a bridge hound goes untreated, the venom affects the body with a chronic disease that develops through several stages. In it's early stage the bitten body becomes hyper active allowing the host to fight past wounds that would normally be mortal but also spreading the venom through the body. The second stage of the disease the body becomes resistant to magic. The third stage, the host is affected by the sickened condition as the venom loses its viscosity and begins to harden throughout the body. Depending on the amount of venom initially transferred to the host, during stage four the host has a chance to be petrified, stalling the spread of the disease. Those who are not petrified have their hit point maximum halved. The final stages of bridgebite result in death.

Mechanics
A creature afflicted by Bridgebite remain conscious below 0 hp until they have taken 20 additional damage, only while in stage one.

The second stage of the disease the body becomes resistant to magic. Each time the creature takes an action, the disease has a 10% chance to progress to the second stage. The affected creature gains magic resistance, and any attempt to magically remove the disease has a 50% chance to fail. If a magical method fails to remove bridge bite, the disease becomes immune to that magic for 12 hours.

The third stage, the host is affected by the sickened condition as the venom loses its viscosity and begins to harden throughout the body. The disease progresses to the third stage if the creature has been affected by the second stage for one day.

After three days of being afflicted with the third stage the creature must roll a percentage die. 1-50 the creature becomes petrified. 51-100 the creature does not become petrified. Those who are not petrified have their hit point maximum halved.

The final stages of bridgebite result in death. Each day the creature remains afflicted by Bridgebite they must make a DC 16 constitution saving throw or die.