Ghouls are abominations with a sapient level of intelligence. They have an unnatural craving for the flesh of living humanoids and their appearance will change depending on whether they satisfy this craving. As long as they don't feed, they will appear very similarly to their original race, with the exception of extremely pale skin and red, blood-shot eyes. As they proceed to consume humanoid flesh, they degenerate into an undead-looking ghoulish creature, full of decay and open sores. A ghoul can survive without eating for a very long time, as their corruption preserves them in a state similar to undeath. During that period, they will slowly revert back to the pale, near-original form.
The condition is transmitted by a ghoul's bite. As ghouls rarely attack or eat a still living person (usually preying on graveyards and fresh victims), the transmission is either fairly rarely or voluntary. Throughout the condition's whole incubation period, the victim suffers extreme feaver and uncontrolled cravings for food. Within the first days of acquiring the condition, it can be treated with leeches who drink the contaminant with the blood. After about five days (depending on the person) the condition can no longer be treated but it takes up to a month until the transformation into a full ghoul is completed. If a victim is discovered in this interminent stage, it should be quickly killed to spare it the corruption and prevent it from claiming its own victims.
After the ghoul is transformed, it bears only passing recollection of its past life. It will use those memories to lure victims if need be, but it prefers hunting for already dead bodies.