Reinforced Wall is a type of impassable terrain created when normal rock walls are fortified. It takes significantly longer to dig through than rock. To be able to be fortified, the wall must be adjacent to the owner's land (claimed path, room, or bridge). Most rooms are made more efficient and cost-effective by having reinforced walls as a border.
Some types of terrain sides cannot be remade into a fortified wall, no matter where it is or how close a player's claimed areas are to it. One example of this are gem seams.
Reinforced walls are impossible for enemy forces to dig through. Unless the enemy has Destroy Walls available to un-fortify them, they are as effective of a barrier as impenetrable rock.
Nearly every type of room (even a Treasure Room) is more efficient when surrounded by reinforced walls.
There is a bug that enables enemies (or at least hero Tunnellers) to breach fortified walls: if an earth tile becomes fortified while being dug, the fortified wall will continue to be dug and eventually broken through, as if it belonged to the other player. However, this is fixed in KeeperFX 0.4.8.2215. There is also another bug that enables you to breach neutral fortified walls while in Possess Creature mode. This is also fixed in KeeperFX, but can be re-enabled as a 'classic bug'; some fan-made levels rely on it for completion.
There are several styles of reinforced wall, but which one you get is not random. The formula for determining which style a wall receives is as follows:
If its position on the x-axis (starting from the top-left) is divisible by 5 and there's claimed path immediately to the north or south, then it's a wall that can hold a torch (though this doesn't necessarily mean that it will have a torch: it needs to have "open" faces). Where the flambeau is depends on the wall's exact positioning.
If its position on the y-axis is divisible by 5 and there's claimed path immediately to the east or west, then it's a wall that can hold a torch.
If its position on the x-axis is odd, not divisible by 5,[Note 1] and there's claimed path immediately to the north or south, then it's a wall with a banner.[Note 2]
If its position on the y-axis is odd, not divisible by 5,[Note 1] and there's claimed path immediately to the east or west, then it's a wall with a banner.[Note 2]
Wall styles according to distance from Dungeon Heart
Otherwise, it's a wall with art. Which one it is depends on its distance from its owner's Dungeon Heart, or, if there's no heart, the top-left tile of the centre four tiles of the map: there's a "ring" that surrounds the Dungeon Heart or centre of the map, another "ring" that encompasses that circle, and so on. The art it gets is determined by which of these "rings" the tile is in.
The checks are performed in that order. The exact appearance of a wall style depends on the tileset. Also, rooms add decorations to reinforced walls, and so may obscure their type. Placing reinforced walls via KeeperFXcheats does not follow these rules, and yields a totally random style; however, from KeeperFX 0.4.9, you are able to force adherence to them by holding right ⇧ Shift.[1]
Dungeon Keeper 2[]
Reinforced walls can be dug through by enemy forces, but it takes a much longer time than digging through one's own walls---especially if the wall's owner has an Imp working to re-fortify the wall in the meantime! It is often more expedient to claim all the path/rooms adjacent to the wall; when the wall's owner has no more claimed path next to the wall, it will automatically un-fortify and turn back into normal rock. Another option is to use the Tremor spell to un-fortify some of the enemy's walls.
