During their Patch 2.0 Campfire Chat livestream, Blizzard announced that Runewords is finally coming to Diablo 4! It appears that the Runeword system will be exclusive to players who own Vessel of Hatred expansion.
Diablo 4 Season 6 PTR Campfire Chat Liveblog
Take a quick look at what Blizzard has been showcasing during the stream down below while we collect all the info: