Who is Diablo?
The Lord of Terror, and what it means that he finally won.
Diablo is the Lord of Terror, one of the Prime Evils of the Burning Hells, and the series' recurring antagonist. This page is an editorial primer, labelled Analysis.
Terror as a method
Diablo's defining trait across the series has never been raw force. It is corruption through fear - working through mortals, through possession, through the people closest to power rather than around them.
Why victory changes the character
Diablo V's confirmed premise puts him on a throne. A being defined by subversion now holds an administration: he rules Westmarch, conscripts a population, and stages an invasion of the High Heavens from captured ground.
That is a different kind of antagonist - and it is also why the confirmed connection between Diablo and the Heir to Westmarch is worth watching closely. Working through an heir would be entirely in character.
The reading above is ours. The confirmed facts are that Diablo rules from Westmarch and that a connection to the player character exists.
