Viking: Battle for Asgard

On the far right side of the camp there's a spot in the fence with no spikes on it. Climb over the fence then turn left. You then jump over a very small fence and you'll see a guy on your right outside a wooden picket fence draging a dead body, wait for him to get close then do a stealth kill on him. Then go through the passage out of the fence to your left and turn left to go up the hill, make sure no one sees you. Stealth kill the guard at the top then kill the next guard with an axe. Hide behind the wall of the next building till no one is facing you then go up the ramp on the left side ot the passage. When you reach the top of the ramp walk slowly and don't attack the guys who shoot arrows, if you walk slow enough they won't spot you. Walk to the other side of the bridge and you'll see the portal in front of you, it should now be safe for you to go to it. Hope this helped.

Well think you're a barbarian , so don't wait

when you enter darkwater
go left , kill 2 working legions
go to the bridge where those archers are , IGNORE them and run further
well go down and run further and climb up until you come by the portal

don't use strategie of fight because it will take you a long time , some enemies will come after you , well once you are by the portal , kill the few enemies that following you
after they are dead
activate the medalion
and go back to the ruins to get your dragon