Instantly dead
 

Hi,

I just began the game and killed every foes on the first island. I discovered the maps and traveled to the two next islands.
But no matter on what island I go, when I enter a battle crowns appear over my characters and I am instantly dead. I cannot continue the game :(

Any clues?

Most likely you have more units than your Leadership can handle. You need to dismiss some units, place them in a garrison in a castle, or get more leadership.

The reasons for the aforementioned could be
a) that you replaced an item that gave you leadership with some item that doesn't.
or
b) that you wear an item that gives leadership but its morale went to 0 so its boni no longer work until you supress its keepers.