The undead of the HOTD universe are collectively referred to as "Them". They do not feel pain, in fact, they don't feel anything at all. They are also blind. However, their hearing is vastly superior to an ordinary Human, which is what allows them to find their prey with ease. Their one and only pray, are Humans. They seem to have absolutely no interest in animals of any kind, other than following the sounds of a barking dog to potential food. The only way to kill one of "Them", they must receive a hard blow to the head, be decapitated, or just have their spine severed. They are also extremely flammable, however, they have been known to survive for a little while after being lit on fire. They will, however, eventually die.
It is currently unknown whether or not they decompose like a normal corpse, due to the fact that unlike traditional zombies which were actual corpses, these are ordinary people infected with a virus transmitted through biting, causing them to act and appear like zombies. It has been noticed that "They" do not run. It is extremely rare that one of "Them" is witnessed running. Their strength is also infinitely superior to a Human being. This is due to the fact that they cannot feel, and thus, their muscles are uninhibited, and adrenaline flows unhindered, granting them access to extreme feats of strength.