How do you write Hephaestus' name in ancient Greek?

Answer 1

You need the Greek alphabet which is somewhat different from the Latin alphabet we use - there was no h in it so that is replaced by an apostrophe; ph was the letter phi, which we don't have a symbol for; ae was ai; us was os.

or

eta phi alpha iota sigma tau omicron sigma

Answer 2

In English, Hephaestus is usually pronounced huh-FEST-uss.