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No, in Enroth, it's original. In general, the Heroes games are mostly an apocrypha in relation to the Might and Magic universe.
Added 2 minutes later
No one touched Sandro from Xeen. The presence of a character named Sandro is a mistake made by 3DO in the Heroes games (they developed them separately from NWC, and that's what happened). Sandro from Xeen's fate is unknown after the end of Might and Magic V (presumably, making him alive again meant he was still alive). Sandro, the apprentice of Etric the Mad, led the Necromancer Guild of Jadama, and when the Reckoning occurred, he moved to Axoth.
Added 2 minutes later
No one touched Sandro from Xeen. The presence of a character named Sandro is a mistake made by 3DO in the Heroes games (they developed them separately from NWC, and that's what happened). Sandro from Xeen's fate is unknown after the end of Might and Magic V (presumably, making him alive again meant he was still alive). Sandro, the apprentice of Etric the Mad, led the Necromancer Guild of Jadama, and when the Reckoning occurred, he moved to Axoth.