Who was a titan who was defeated in battle and buried under mount etna by athena

The two fought a cataclysmic battle, which Zeus finally won with the aid of his thunderbolts. Defeated, Typhon was cast into Tartarus, or buried underneath Mount Etna, or the island of Ischia. Typhon mythology is part of the Greek succession myth, which explained how Zeus came to rule the gods.

Enceladus is your answer.