1.) Be nice!! Be kind!! Treat others as you would want to be treated!! Do not curse! Do not stop doing your job in the mission because you are mad. Do not leave the mission for any reason!!
One of the other big problems with the mission is that people do not know how to be kind to the other players on the team. They swear and curse and eventually someone leaves. Then you are stuck. Because you have to have everyone to participate. Everyone has to be working together. If one person decides to stop healing because they are mad or if another leaves because of something a person said to them then that impacts the entire group and you can kiss the mission goodbye. I've seen it happen way too many times.
Also, leaving the team in the middle of the mission for any reason at all, other than your computer crashed or a technical glitch, is one of the most rude and inconsiderate things a player can do. It impacts everyone on the team. You cost everyone to suffer for something that one person says or does that you do not approve of. So, do not go down to their level. Stay, fight, and do your part. Every time a person leaves the mission, I just want to find them, go into PVP mode, and give them a good hit or two. It's so rude to leave in the middle of any quest or mission. When you agree to join a group then you are giving your word and honor as a gamer.
2.) Protect the King! Protect the King! Protect the King! If the King dies then the mission is over. End of story.
3.) Call Out What You Are Killing. Make sure everyone focuses on their killing strategy. Up until the fight with the boss, you may want to consider killing one beast at a time while protecting the King. If you do then they will go down faster; allowing you to move faster in the game and be more productive. However, once you get to the end of the mission where you have to defend the fort and the King, then it is important that you have a really understood strategy. If the entire group focuses on one beast at a time at the end of the mission then you are all dead. Split up into two groups. One group mans the East side. One group mans the West side. There should be one caster on the East catapults and one caster on the West catapults. It is the job of the casters at the catapults to do two things. First, they must tell the others who are on "front line" when incoming attacks are approaching. Second, they must keep those catapults moving!!
Whatever you do, do NOT run outside of the fort area. Let the bad guys come to you. Do not run outside. When you run outside you are really exposing the fort and the King and the casters. Stay together. Fight together. Work as a team and there is no doubt that you will be successful.
Oh, I almost forgot. If your team needs a second monk and are wondering about whether or not to take one of the henches, here is my recommendation and I'm providing this information from my own personal success and experience. Take Menlo with you if you need another monk. He is the better of the group and can serve you well. But make sure you don't completely rely on him. He is a hench after all.

4.) Pick a Leader!! Ask your team if anyone has completed the mission before. If they have, and are just there to help out a friend, then let them lead. They know how to beat the mission so listen to them and follow directions. If a person says that they have "done" the mission then that does not mean they actually "beat" the mission. In otherwords, they died and are back to try it again. So, they really do not know how to "complete" the mission because they have not finished it yet. But, if you have no other options and if nobody in the mission has completed the mission, then listen to the one or two who has actually "done" the mission and pick one of these two to lead. Do not have both lead. Pick ONE!! Then, follow directions. You need to make sure that everyone is clear about who is leading the group.
5.) Turn Right at the Y in the Road. When you first enter the mission you will face three big elephant beasts. Kill them and then you will come to a Y in the road. Turn right!! Do not turn left. Then go up the hill and turn left to kill the three ice beasts on top. The ones that you avoided by going right will still be there and will not be attacking yet because they don't see you. This allows you to take one group at a time and reduce the amount of damage you take as a team.
6.) Pull to the Bridge. Once you get to the bridge, pull the beasts from the other side onto the bridge. Then stay on the bridge and take the beasts down. If you do not pull the beasts then the patrol that will come up behind them will also attack you and probably outnumber you. You want to take the least damage that you can and reduce the risk of damage to the King. If even one person dies in the mission before the end then that person will have a Death Penalty. You can't afford a death penalty at the end of the mission.
7.) Skip the Bonus. Do It Later. Unless you are a top notch experienced team who plays together extremely well (perhaps you are in the same guild) then I would HIGHLY recommend skipping the bonus. Otherwise, 9 times out of 10, the group will die and the mission will be over.
8.) Place Casters at Catapults. Okay, when you get to the end, there will be beacons and catapults. Make sure you do NOT light the beacons otherwise you will be summoning more bad guys to come your way. Also, lighting the beacons is the bonus quest. Like I said before, I would suggest skipping the bonus and doing it later once you have completed the mission. So, leave the beacons alone!! Now, that brings us to the catapults. You need two casters manning the catapults. To man the catapults that means staying with them and making sure they are firing. To fire a catapult, simply run from one catapult to the other and pull the levers. But here is the key. Someone, and I mean only ONE person, must be at the catapults at all times. If those catapults aren't moving then someone isn't doing their job. You will need all the help you can get.
Now, why do I say have "casters" at each catapult?? It's really simple. You need casters because they can still do damage to incoming attacks by casting downward from the top area where the catapults are located. While they are casting down they can also SHOUT OUT what is coming from each side. This way you will know, in advance, what to expect and can form your defense accordingly. If you have anything else other than casters at the top then you will not be doing damage to the incoming attacks. You have to do both damage and SHOUT OUTs to be successful up there.
9.) Cover The Area. Next, you will be faced with a boss at the end. The hardest part of this entire mission is the fight with the PERFECT AMOUR. This is a lvl 28 beast that hits hard. His objective is to take down the King. So watch yourself. You will have them trying to get to the King. Most of the time, they are successful and the mission is over and you are defeated. The reason why they are successful is because of poor teamwork, failure to man each doorway (east and west), someone left the catapult area when they were supposed to be up there, etc. Remember, casters can cast downward so keep them up high so they don't take damage. You want to minimize the amount of damage that your team takes while doing the most amount of damage you can.
10.) Do Not Rush Mission. Also, do not rush this mission. Take your time. Think about it - What would you rather be doing? Would you rather take your time, form a strategy, get the team together, and beat the mission? Or, would you rather rush it and kill each mob one after the other without letting your team heal up and get their energy back and then eventually start dying and taking Death Penalty? Sounds stupid when you think about it but way too many teams rush the mission. I can't tell you how many times a group will yell out - What is your problem! Come back! Oh Crap!! Take the bottom!! Take the bottom!! Do not rush!! You have to play as a team. You MUST!!!
11.) Pick Up Drops After Fighting. Okay, now lets talk about drops. A drop is an item that appears with your name on it after a bad guy goes down. Too many players will stop fighting when a drop with their name on it appears. They figure - Might as well get the drop now in case we die! When you stop to pick up a dropped item, you cause yourself to take damage and to inflict zero damage to the bad guy who is hitting you and trying to kill you. Also, you risk your team as well. So, wait and clear the area first. Then go and pick up your drops. They will still be there.
12.) Fight Strategically. Okay there is one part of the mission that I forgot to talk about. This part is when you enter the city area and there are two levels of bad guys. There is a bottom level with a group of bad guys. There is a top level with bad guys. The top level is blocked by a door that the King will open when you walk him up there. Here is my advice. If you want to do less damage to the team, protect the King from harms way, and ensure that you get past this part without having to rez a team member then here is what you do. Everyone, and I MEAN EVERYONE (not almost everyone while two others go up and unlock the door), stays down below. From below, there are two groups of bad guys up top. One on the right and one on the left. Take out the group on the right first. You will see them. Have all of your casters cast upwards from down below. Protect them with healing and spells. Warriors do nothing! Nobody goes up top. Everyone stays down. Cast up and kill the group on the right. Then repeat the same thing for the group on the left. Once you are done you can sit back and rest happy that you didn't risk or expose your King to any damage and you didn't have to rez anyone either. Then, once both sides are taken out, go up top and pick up the dropped items. Then heal, max out your energy, and take on the last group right before you get to the area where the final part is located.
Well, I hope this helps everyone. I know it's a lot of information to take in but I hope it's useful. Just remember that this mission is not like the others. It is strategic. It tests your ability to think, work, and act as a team. So, pick your leader before the mission begins. Get two monks and two casters if you can. You definitely need two casters. One monk will suffice but they must be willing to do nothing but heal, heal, heal, heal. They can fight when they have to but they must be healing too, especially the King!! Okay, two monks, two casters, you definitely need a strong tank or two, and you need one person who can pull (for the bridge fight). Then, for the remaining slots in your team, just fill them with warriors. Also, you may need the Rebirth spell and lots of smithing!! If you can return damage back to the original source when you are hit then that is awesome. Also, if you can rez a lot of minions to help out then that is also great.
Oh, one more thing before I end this. The question is - Is it worth finishing this mission? The answer is YES! After this mission, you get to the Fire Island where you can take down the mantle and enter the RING OF FIRE. So yes, definitely, you want to finish this mission. And, just in case you are wondering, I DID COMPLETE THE THUNDERHEAD MISSION.
Hope this helps everyone. Take care and good luck in the mission. See you on the other side!!