Final answer:
The dragon first appears when Ethelred enters a palace and finds it being guarded by a scaly and fiery dragon. Ethelred eventually slays the dragon with his mace.
Step-by-step explanation:
The dragon first appears in Beowulf when the champion Ethelred enters a palace and instead finds a scaly and fiery dragon guarding it. The dragon is described as having a prodigious demeanor and a fiery tongue. Ethelred eventually slays the dragon with his mace.