I don't remember exactly where the music came from... but I think the selection didn't go beyond Might & Magic X, VI, and VII.
You can defeat Valentine, but he will resurrect. It's not recommended only because he is a very dangerous opponent. Center Perk, Light, unique tier 6 warriors, etc.
There is a timer in the mission, after which the red player's troops (Kolger and Lorik) become significantly stronger. There seems to be a notification about this, as well as several hints.
You could say that after the streaming incident, my mapmaking activity for the fifth game came to a halt.