How is Dark Messiah connected to Heroes of Might and Magic?

The creators of the heroes made a regrettable blunder!!!!
Who guards Nicholas's mausoleum and who does Agrail kill upon entering this mausoleum????? - Laslo.......
Who is Fiona's first assistant in the Hammers of Fate?? - Again, Laslo!!!!

And still, how did Sareta's heart end up with Arantir???