As fausts are technically still human they look almost exactly the same as before they forged their contract, however hunters have found a few small differences similar to those of demons. Their finger nails grow slightly and become sharpened, and their skin begins to pale giving them an appearance similar to a vampire. Their ears also begin to develop a very small point, and their teeth become slightly sharper. The largest and most noticeable difference is their eyes, as their pupil becomes slitted and their eyes actually become a blood red color. In the few known cases where fausts have survived their contracts, their eye color has been known to go back to normal however their other differences remain. Black horses also bow to fausts, and they seem to be under the command of the faust similar to their contract.
While fausts can technically be injured quite easily, this almost never happens as their contracts are extremely protective of them, not wanting anyone to kill them and free them from their Faustian Contract with them. However, if you can disable or trick the demon it is quite easy to kill the faust.