Every time I talk to cain in Act 4. He says the line “The time has come to destroy mephistos soulstone…” I have soulstone in my inventory but cannot insert it to Hellforge. The quest is active and read “Destroy Mephisto’s Soulstone at the Hellforge.”
Are you trying to use the one he gives you, or one you picked up from Meph? If you’re trying to use the one Meph drops, just get rid of it, take the one Cain gives you and give that a try…?
This worked, thanks. Could not identify anything after killing diablo before trying this.