Final answer:
Grendel resides in a gloomy swamp and has a monstrous appearance, inspired by Anglo-Saxon and Norse mythologies.
Step-by-step explanation:
Grendel lives in a desolate and dark swamp that is sometimes described as a cave. He emanates from Anglo-Saxon and Norse mythology and is notably featured in the Old English poem Beowulf. Grendel's appearance is depicted as frightening and monstrous, often being represented as a giant or troll-like figure with perhaps some human characteristics, symbolizing malice, darkness, and devastation.