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

Kha-Belekh ordered him to kill Nikolas. Agrail didn't want to do it if possible, but he still wanted to take the place of the Overlord, so betrayal wasn't in his plans yet. He attacked Isabel with a tiny army. Besides, he still managed to trick them. He was supposed to deliver the captive to Shio immediately, but instead, he hid the queen near Danmur, giving Godric a chance to save her. He was just pretending, but in reality, he was trying to save both the queen and the king. It didn't work out... Nikolas turned out to be, as Tieru said, a "brave fool".