It took me a long time to be able to survive The Valley of Death in the Heir to the Throne campaign (I am talking about Battle for Wesnoth in case you didn’t read the title). Because of that I’ve always had a lot of respect for this particular episode and consequently anytime I get to The Valley of Death I just send all my units south, defeat the lich and stay put until the rounds are up. Occasionally I send a few units to gain some extra experience by knocking off a few walking corpses coming from the east.
The other day I decided to try to defeat all three liches. It turns out to be quite simple. This is what I did.
I sent my three white mages up north. They are efficient against the annoying wraths. With them I sent Delfador to act as a backup in case my mages run into trouble. After a few battles with wraths, one of the mages becomes a Mage of Light. I get my second Mage of Light by defeating the northern lich.
To the east I sent my three horsemen and Kalenz. One of my horsemen was a Grand Knight, the other two level two knights. These two quickly become level three characters as they get attacked a lot. The three horsemen take care of all the walking corpses easily. Although there are many of them they do little damage and the horsemen are strong. When I horseman needs to heal he runs to a village and Kalenz temporarily steps in. Kalenz is of course mostly useful, but can buy some time while a knight heals.
In order to separate the walking corpses I spread the horsemen out so that one attacks from the North, one from the West and one from the South. Kalenz stays behind to the West, but ready to move where he needs to. When I’m ready to kill the lich I entice him to attack my Grand Knight who has full hit points. Then the other two horsemen ride in and destroy him.
To the South I sent my three red mages. One quickly becomes an Arch Mage and one other gets is just 4 points from promotion at the end of the scenario. Because the units can take quite a bit of damage from the enemy units in the South, I also had brought two elvish shamans along. In addition, I recruited one scout to cause distractions and prevent all enemy units from attacking my mages all at once.
I used my new Arch Mage to soften up the southern lich, and one of the red mages to deal him the final death blow.
What about Konrad? Well, I sort of forgot about him, and left him in the middle. My Konrad is a level three character, so I would probably have sent him South to act as an additional backup, had I remembered him.
Now that I’ve lost my respect for the Valley of Death, I’m going to try again with a few changes. First of all, I won’t use my Grand Knight. It’s better to my level one horsemen so they can gain some experience. Second, I’ll let Konrad go South instead of recruiting the scout. He will be responsible for creating a diversion.
I also think I’ll send two white mages and a red mage up north, and let the third white mage join in to the south. That way I have one unit that can heal there and won’t need the shaman anymore.
A few tips
First of all don’t get close to the liches with units that are injured. It’s a quick way of losing them, as the lich will attack a weak unit. As a matter of fact avoid confrontation with a lich during the night (they are hard to defeat then). When you do attack, it’s a good idea to have a powerful unit (Defaldor, a Mage of Light or an Arch Mage) standing by, just in case they need to step in. Once you begin your attack on a lich you should finish him off before he gets a chance to counter-attack.
Keeping the white mages together in the north is a good idea, since they heal each other.
In the South you really need to position the units carefully to avoid a single unit being attacked by multiple enemy units at once. This is also true to lesser degree to the North. To the East however, you will want to place your horsemen where they can act like “corpse magnets”. The more the merrier.
When you are recruiting/recalling, make sure you position the units so that they can move as far as possible in the direction they are going. The key to success here is a swift attack, at least to the North and to the East. You shouldn’t let the wraths get a chance to get away as they are way to quick for a mage to keep up with. I held back a little more to the South, where I used the scout to try to as far as possible single out enemy units and take them out one by one.
Obviously how you play will depend on what type of units you have. I tend to use mostly mages on Isle of Anduin, Muff Malal’s Peninsula and Seige of Elensefar. At the Bay of Pearls my horsemen get a lot of battle experience. On the Princess of Wesnoth episode, I use a combination of mages, elvish rangers and horsemen to attack from different directions. That way, by the time I get to Valley of Death I already have some experienced mages as well as horsemen.