Riverside Province (mission)

Primary
Collect the Scepter of Orr and escape

You can complete this mission with killing almost no White Mantle. Simply keep hugging the left wall, and with a compact group, and correct timing (waiting where necessary), the mantle will not see you. At each tower, hug the left and you should be past (and through the gate where appropriate) before the mantle spread out and block the path. Since the mantle are in large groups this can be a much easier way through the mission.

After collecting the orb, pass through the gate and again keep hugging the left wall. Eventually you get to a pair of towers surrounded by loads of White Mantle. Look carefully and you will see a boss, and a narrow bridge between the towers. Pass quickly through the mantle, kill the boss, and pass along the bridge to complete the mission.

Bonus
Kill all the Watchtower Guards (9 of them) - one up in each tower. Usually this would involve killing nearly all the White Mantle surrounding them, as well as the White Mantle Seekers standing next to the Guards up in the tower. Try to pull very carefully - about 3 at a time since otherwise they will overpower you. It may be worth working to the port, and then back to the Scepter since that way you only need one survivor to complete the mission itself for you in case of a wipe. You may also be able to resurrect the party by talking to the guy who hands you the Scepter of Orr - if you can get to him.

At the first watchtower you'll see some guards having a short conversation. After a while all of them will spread out in small groups around the tower. Keep a safe distance from the tower, otherwise they'll all be called back. Pick off each of the groups until there are just a few stationary in front of the tower (two Savants and two Justiciars). Kill them, then kill the guys up on the top of the tower. You'll have to do it from the ground since you can't get it. Make sure to have decent ranged attacks for here, as they will have some sort of health regeneration you'll have to work against. After you do so, talk to Saidra who should be nearby, and she'll give you the bonus objective. The gate will open, and there will be another tower. Use the same tactics on this tower and the rest in the mission.

Tip: The White Mantle up in the Tower in fact can be attacked with melee weapons. You have to walk up as close to the front gate of the tower as possible. From here you also have a chance to recover items dropped on top of the tower. This doesn't always work, though.