Proceed to the teleport with all three vikings. Shoot the red switch on the left with Baleog's arrow to stop the rotating shaft and switch off the electric fence. Then move left and fall down with all vikings, jumping for the two bombs with Erik at the top left. Carefully pass the electric fences. Use a bomb on the floor at the right. Then fall down with Olaf to protect, and kill the electric enemy. Then proceed to the teleport with all wikings.
Glide through the pit using Olaf's shield (don't fall down yet!), and jump across with Baleog to land on top of Olaf's shield. Shoot the switch on the right, and proceed to the teleport on the left with Baleog. Jump down the pit with Olaf (avoid the two electric fences), then jump across the room collecting the red key. Press the red switch at the bottom right to switch off the electric fence below, and proceed to the teleport.
Now time for Erik - jump across the pit to the teleport at the top. This takes him below where Olaf was collecting the red key. Jump across the electric bridge, and release the bomb mid-jump in the air to destroy the floor blocks under the fence. Proceed to the teleport. In the new room, jump across the teleport to collect the bomb, and jump down to the left. If you arrive at the elevator field at the right speed/angle, he will easily fall down. Use bomb on computer at the bottom. Then go back up, and fall down on the right side (electric fence now defunct).
Once you're down at the bottom with Erik, pay attention very carefully, as this is a hard part. You'll have to avoid fire balls, so be careful with timing. Pass to the left, then go up. In the second floor, there are fire balls and electric fences, and the yellow key. (Note - the yellow key sometimes didn't appear for me, maybe a bug?) Then go on to the right. Now pay attention very carefully, as there's electric fence at the top right! So you'll have to immediately pass to the left as the elevator field lifts you up, and dodge the fireballs, otherwise you're dead. After you're on the left side on the 3rd level, steer towards left to avoid hitting the electric fence. Then go on towards the teleport which takes Erik back to the beginning of the level.
Now proceed with Baleog. After teleporting, jump down the pit and jump across the room at the bottom using the springs, meanwhile switching the 2nd and the 3rd switch using the S key to switch off the elecric fences above. Do NOT switch on the 1st switch! Leave it off. Then jump to the teleport on the right, and use it. Climb down the ladder, and jump on the moving platform. Hit the switch on the top with an arrow, then proceed to the next ladder. There are two electric enemies here - best strategy is to jump down when he's away, shoot an arrow, then climb back up the ladder to avoid his lightning strikes. Carefully kill both electric enemies. If they hit you on the ladder, Baleog will fall down and they can hit you again - you're dead.
Once you're down, pass to the right (electric fences should have been switched off), collect the blue key and use the teleport which takes you back to the beginning of the level. Once there, stand below the red switch with Olaf, holding his shield up. Jump on top of his shield with Erik, and jump up to switch off the red switch. This turns off the electric fence on the right, and you can proceed to the exit. Use all keys to open exit door, and voila. You just finished a really hard level.