Spoiler alert! Don't read if you haven't completed the original Diablo from 1996.
At the end of the original Diablo, the hero shoves Diablo's soulstone into his or her forehead. That ending is identical for any hero choice. Is there a canonical "which hero it was" fact in Diablo II? e.g. do we know that it was a warrior that used the soulstone, and subsequently became the host for Diablo's new form?