"Ghouls are stronger than most risen dead, but they gain their fortitude through horrific means — feasting upon human corpses. These creatures are least dangerous while eating, but do not disturb them or it shall be your limbs between their teeth."— Deckard Cain(src)
Ghouls fulfill a similar role to Zombies from previous games, but have faster movement and attack speed. They are blue-skinned undead who spawn in great numbers, are quite fleet of foot and quick of movement, but are fairly weak and easy to kill. While ghouls often fight empty handed, some have been seen wielding swords. At many times, they will climb up the walls to ambush the player.