I've been messing around with Racthoh's War + Hero farming, and I figured I could mess around on my Derv to do the same for Tombs. So here you go, a Dervish build possible of killing everything all the way up to the end.

Your Bar:
[skill]Victorious Sweep[/skill][skill]Mystic Sweep[/skill][skill]Chilling Victory[/skill][skill]Conviction[/skill][skill]Vow of Silence[/skill][skill]Heart of Fury[/skill][skill]Mystic Vigor[/skill][skill]Mystic Regeneration[/skill]
Note: Make sure you use one of these secondaries:
/R, /N, /Me, /A, /Rt, /P
If you use /W, /Mo, or /E, Fingers of Chaos will mess completely with your build. Btw, ignore what it says on the last sentence. It's false. Crip and Blind does NOT affect Dervs. I've farmed this at least 10 times (It's reeeeeaaalllly long. >.<), and I've never been hit by either.
Your Attributes:
Scythe Mastery: 16 (12+3+1)
Mysticism: 11 (10+1)
Earth Prayers: 9 (8+1)
Your Equipment:
Scythe 1:
Ebon/Fiery/Shocking/Icy
+15% Damage (while enchanted)
Enchantments last 20% longer
Scythe 2:
Zealous
+15% Damage while enchanted)
Enchantments last 20% longer
Set 3:
Any longbow/flatbow will work. I use a stormbow that I picked up.

Armor:
Max Armor
Windwalker's Insignias.
Superior Scythe
Minor Earth Prayers
Minor Mysticism
Optional (I have a Minor Wind Prayers here, because I just use my normal Derv set. :P)
Minor/Major/Superior Vigor, any will work.
Talkhora's / Dunkoro's Bar:
[skill]Blessed Signet[/skill][skill]Life Barrier[/skill][skill]Protective Bond[/skill][skill]Life Bond[/skill][skill]Balthazar's Spirit[/skill][skill]Essence Bond[/skill][skill]Succor[/skill][skill]Rebirth[/skill]
Note: Before you say anything, I've done some testing with Prot Bond. While using it in this build, it pretty much prevents you from taking too much damage, while not triggering that often. Examples are: Energy Surge, Wurm Siege, The Darkness, etc.
Talkhora's / Dunkoro's Attributes:
Protection Prayers: 16 (12+3+1)
Divine Favor: 13 (12+1)
Talkhora's / Dunkoro's Equipment:
Anything weapon will work. My Talkh still has her starter set.

Armor:
Full Radiants (Not really required, if you're poor)
Superior/Major Protection Prayers (Major works just as well)
Minor Divine Favor
Rest is optional
There are four things you'll need to know to perform this build:Know Your Enemies
You'll have to know what to use when fighting what. Here's a list of all the enemies in Tombs and how to fight them.
Grasp of Insanity
http://gw.gamewikis.org/wiki/Grasp_of_Insanity
This is one of your main enemies in Tombs. You can effectively tank about 9-10 if you're careful. [skill=text]"Fear Me!"[/skill] will knock down your energy if you're tanking that many, so pull out your Zealous. If you're only fighting one or two, use your Elemental, because that they're wars, you'll do way more damage.
Scythe of Chaos
http://gw.gamewikis.org/wiki/Scythe_...s_%28Mesmer%29
This is another one of your main enemies in Tombs. They have Spirit of Failure, which can be very annoying, so if you want to speed things up, use Vow. From experience, I've found they're weaker to my Elemental than to my Zealous.
Banished Dream Rider
http://gw.gamewikis.org/wiki/Banished_Dream_Rider
These little suckers will be your worst nightmare. Go for them first, unless you're in Level 4. I'll explain later. But for now, keep Vow up, always. If they're in their Terrorweb groups, you don't really need any healing. But if you're fighting them in their mixed groups, hit Mystic Vigor, Mystic Regeneration, then Vow. It'll more than likely remove Mystic Regeneration if it gets a spell in the 3/4 second Vow is down, but Mystic Vigor will keep you alive. Just like the Scythes, I've found them weak to my Elemental. They're also one of two Ecto Droppers.

Terrorweb Dryder
http://gw.gamewikis.org/wiki/Terrorweb_Dryder
Easy. They're weak to your Zealous, just keep Vow up at all times, and they can't do anything. These dudes are your second Ecto Droppers.

Chained Souls
http://gw.gamewikis.org/wiki/Chained_Soul
You can fight in the aggro-range of these weaklings, but you have to keep Vow up at ALL times. Otherwise, avoid at all times. Also, try to time when they die and when they spawn. You don't want to be in the aggro-range of a Soul when they spawn, or it'll catch you offguard.
Chaos Wurm
http://gw.gamewikis.org/wiki/Chaos_Wurm
There are two versions of these big things, Burrowing ones and Siege ones. You'll encounter Burrowing ones in Level 2, 4 in total. Siege ones will be all over Level 3 and 4. Burrowing ones are easy if you take them alone. There'll be instances when they're with groups, just pop them and pull them away from their group. To see if they're following you, just look at that big black dust cloud following you.

Know Your Pops
I know all of my pops from my time as a B/P ranger. There is a ton, but I can't really show them all to you, as I don't have a map or anything. Just a piece of advice, in the middle of Level 2, there will be two patrols, two pops, and two wurms. So pull carefully.

Make sure your Bonder is on your Compass!
Don't wander too far away from your bonder. Make sure you flag him/her to a safe location whenever you fight another group. If you do go too far, you'll lose your bonds. And if you're in a middle of a battle, that's not what you want happening. >.<
Know how to group your enemies into a ball!
Your scythe has AoE, which can attack up to three enemies at once. Use this to your advantage and ball them up into one big group in front of you (Not around you, Scythe AoE only hits those in front of you). You'll be doing so much more damage this way.
The Farming:
Okay, go to The Tombs of the Primeval Kings, then enter that big black portal thingamajiggy.
LEVEL 1
Shift click all the skills on your Bonders bar except Blessed Signet. Have him/her cast all the bonds on you IN ORDER, then use Balthazar's Spirit on herself/himself. Then flag her away. If you're an experienced B/P, this should be easy for you. Pull the first patrol, you'll notice it. Make sure you pull them far enough so you won't aggro them to the Zashien dudes behind you, but far enough that you won't aggro the groups near them if you attack the Scythes. Attack the scythes, then the Grasp. After that, there's a pop of three Grasps to the left of the first bridge. Get them to come up, then pull out your Zealous and spam your attacks. They should go down pretty fast.
Okay, now pull the group near the Chained Soul in the center of the map. Note that there's a pop near that group, too, so pull them far enough so you won't trigger them. If you can't accomplish this, then just kill the Grasps first, then pop the group (Make sure the Chained Soul is dead and/or you have Vow up) and try to pull them away from the Soul, then fight them all. Now, go back and around to left of the bridge, then continue to pull either the patrol of grasps/scythes or the group of Terrorwebs. Finish them both off, then continue to pull the group in front of the stairs that leads up to the huge mob. They're pretty simple.
Now, go back around, up the bridge to the center Chained Soul (make sure he's dead and/or you kill him with Vow). Now, this part will be hell for new people to this run. Three Riders and three Terrorwebs. Put up HoF/MS/MR, then Vow. Go for the Riders first. One MAY kite, I'm not sure, since I haven't tried it since Hard Mode, where they updated the kiting stuff on Normal Mode creatures. Keep Vow up at ALL times. Eventually, you'll kill them, and then go for the Terrorwebs. As an alternative, you can pull the Terrorwebs or the Riders and kill them off instead of taking all 6 at once.
Now, time for that huge mob. Put up HoF/MS/MR, then Vow, then pull them away from the Chained Soul. Ball them up, and take down the Grasps, then the Scythes. Yay, time for Level 2!
FYI: You'll need to try once or twice if you're new at Tombs, so don't give up right away if you fail. This level only takes 20 minutes or so.
LEVEL 2
Bonds on you in order again. Flag your bonder to the back of the little cave you're in. There should be a patrol of 2-3 Riders and 2-3 Terrorwebs near you. Pull them, but don't head back into the cave, but near the entrance. Make sure you have Vow up. Take down the Riders, then the Terrorwebs. Now, go around the center part, and pull the patrol. Make sure you take your bonder with you and flag her somewhere safe. This patrol is your Grasp/Scythe group, so they should be easy. Take them down. Now, go into the second cave. There's a group and a pop. If you're experienced, aggro them both, take the grasps outside the cave and avoid the scythes' wands with the wall. If you're not, try to pull each separately. Now, for the center piece of that area, there's a group, a pop, a Chained Soul, and a patrol of Riders/Terrorwebs. Go back around to the starting point, flag your hero, and pull the stationary group. Finish them, then pop the hidden group, pull them back, and finish them, also. Make sure the Soul is dead before you pull! Now, charge into the group of Riders/Terrorwebs, and kill them off with the strategy you used before.
The center of the map. Fun. Pull a patrol, kill them, pull the other, kill them too. Be sure not to go ANYWHERE near the center of the center, where the altar is (The Soul originally there has been replaced). After you kill them, move very slowly into the center. If you see ANY red dots on the map, run to your bonder, making sure you flag her farther away when you get to her if there's still the groups following you. Now, on the map, you should see maybe 1-2 groups and 1-2 wurms. Pull the wurms, making sure you don't lose the aggro of the wurm, but lose the aggro of the group. Finish the wurms with HoF and MR, and spam your attacks. Note when Wary goes up, when it fades off the screen, spam your attacks, and/or if you see the wurm use a skill while in Wary. After that, pull the two groups in the middle. Now head north.
There's a group of Rider/Terrorwebs. Kill them as you have before. Now, there's a HUGE HUGE HUGE mob in the north area, with many pops. Try to pop the groups first and fight them, then pull the patrol. Note that there's a Soul in the middle, so pull/pop carefully. After you've killed all the groups, clear the group to your left/to the west. Note that there IS a wurm here. Try to pop the wurm without aggroing the group and pull it. Kill it like you have before. Then kill the group. Head back to the center of the map with your bonder, then head to the southwest.
Terrorwebs. Lots of them. There are 2-3 pops right in front of you, so pull with Vow. The Terrorwebs won't be able to do anything while you're in Vow. After you've cleared the group, keep Vow up, and watch the patrol around the Terrorwebs. Once the left entrance is patrol-free, head around, and kill the two Terrorwebs up there. By now, the patrol will more than likely be back, so kill them, too. Now, kill the rest of the Terrorwebs, then kill the second patrol. Now, there's one last group, with a wurm, in the right cave/southeastish cave. Try to pop the wurm, pull it, kill it, then kill the last group. Now, to Level 3!
FYI: You've just finished the longest level in the run. Congrats.
LEVEL 3
You should be experienced enough now to know what to do in battle, so I'll just explain the route and how to fight mixed groups. Before the kiting update, Terrorwebs would usually kite, so don't go for them first. Go for the Riders, then the Scythes, then finish off the last two. Go to the left, pull the patrol. There's a second patrol that's gonna travel along the bridge, so note that. When you finish the first patrol, take out the second. Now, there's a wurm. Get to the cliff nearest to it, and pull the patrol nearest to you. It should travel around and up the stairs. Finish it. Go near the wurm to pop the group near it, then pull back, finish it. Then kill the wurm. Note the patrol to the north, try not to aggro them. Keep Vow up while fighting the wurm, too. Now, kill the patrol. Continue north and around the corner. You'll notice two patrols. They'll squeeze onto the stairs, so pull the one nearest you and pull them back as far as you can. Kill them, then pull the other group.
Once you've finished them off, kill the wurm nearest you. You might get a few aggros from the huge center group while you kill him, so finish them off. Once you've killed the wurms, pull the groups around the center of the map one by one. Then kill them. After you've cleared the center, go near the second wurm. There's a pop here. Kill the pop, then kill the wurm. After you kill the wurm, pull the group nearest you, which travels from the wurm in the distance under the bridge and near the stairs you're close to. Finish them, go down the stairs, then up the stairs to the right and kill the patrol up there. There's a second patrol not that far away, so kill that one also. Note that there ARE pops in this area, but you don't have to kill them to continue.
After you killed all the patrols, go down to the last wurm and kill it. There's a pop here, so try to ball up the wurm and the group here so you can kill them all at once. Now, we continue on to Level 4!
FYI: All pops in this level are full of Grasps.
LEVEL 4:
You'll start off in the most difficult situation ever. Bond up, then flag your hero to the corner. Wait till the patrols go away to pop the group down the stairs. Kill them, making sure not to aggro ANY of the three patrols, then head back. This part IS difficult. Follow the patrol to the RIGHT, DOWN the stairs, which is near the wurms. Kill the Scythe first, the Rider will run like hell (Before kiting update). Then kill the rider, then the grasps, then the Terrorweb. If you don't have Vow up, the Wurms will bomb you, so make sure Vow is up at all times. Head back to the beginning point. Follow the center patrol up the middle stairs now, and kill them in the same manner you killed the first. Head back, and kill the patrol to the left.
Continue up the stairs and head to the north part of the map. You'll notice a patrol, pull and kill. There may be a pop here, I'm not sure. If there is, make sure. If there's not, pull the group that's up the north stairs. There's a pop around them, so be careful. If you aggro both, make sure you react quickly and take down the grasps with all your enchants up. The bridge should be down now, so cross the area over to the wurms and kill them, making sure Vow is up to prevent the sieges from killing you.
Fun part. You can pull the whole group at the bottom, or pull them one by one. Your choice. Just make sure you fight the group in the area between the two souls. After you've cleared the whole center, kill the wurm, being aware of the pop around it. Head up the east stairs, and pull the center group. After you kill them, wrap around and pull the group on the right, making sure Vow is up/the Soul is dead while doing so. You don't have to pull them, but make sure Vow is always up when fighting in the aggro-bubble of a Soul. Then go to the left and take them out, you should be out of the bubble of the Soul now. The bridge should be down, so head over to where to last wurms are. You can see the Darkness from here.

NOTE: BE SURE TO FLAG YOUR HERO CAREFULLY. The Z Axis is screwed up on bridges, so if flag her by compass, she'll go around and below the bridge, aggroing EVERYTHING. Make sure to flag her by means of clicking the bridge manually.
Pull the group to the right/south (if you're facing a different direction than east) and kill them, too. Make sure not to pop the group down there. When you've finished them, pop the group and kill them. Now, it's time for the Darkness!

Pull the Darkness' group, and kill off the grasps, then Terrorwebs. In some cases, the Terrorwebs are wimps and you can't kill them without chasing them, so go for the Darkness in that case. Try to ball them up, and make sure you're not in Diversion while casting Vow! Make sure you have Conviction up, as they have some hard wand damage. >.<
After they're dead, congrats! You probably got some neat greens!

TEH LOOT
Money
Globs of Ectoplasm
Blues/Purples/Golds
Greens!
Make sure you bring an ID Kit, and 1-2 Superior Salvage kits! Have fun with the run!

FYI: This run will take 2-4 hours for experienced people, and about 3-6 hours for new people/people who go afk a lot (me :P).
Also, I'm trying to figure out a way to use something like this in Hard Mode, but they trigger Prot Bond WAY too often. Any ideas?
