Marlblood is a blood scenario.(like myth blood, except ordinary units) units spawn automatically, and will upgrade to a better unit every 50favor you gain. You gain favor by fighting, so obviouslly you MUST choose a Norse civ for the game to work. If you do not choose a Norse civ, you do not get upgrades and then you will lose :( the map was originally created for 8 players but I have changed it a bit for 4 players. You have a hill fort, and if that hill fort is destroyed, you lose the game. every 5 minutes there will be a mini-game* and a chance for you to win some god powers. another cool feature is if the walls protecting your area are destroyed, minions appear underneath the fallen walls to defend.
*the mini games are similiar to TTF racing for AoK, or something like MarioParty for nintendo I suppose :)
try them out they're very fun.