It’s very difficult to prove a negative, but I am reasonably confident that no rule in 3.5 or Pathfinder explicitly states that all armors of a given weight class slow you down by the same amount. In 3.5, at least, there were certainly a few super-heavy armors that reduced the speed by more than your typical heavy armor (Races of Stone had a couple of these).
So yes, every Medium or Heavy armor must somehow explicitly state its own speed reduction, even if the overwhelming majority of them have the same speed reduction. On the other hand, if a given case failed to do so, I’d just chalk that up to the designers not realizing there was no such general rule, since it usually is so consistent and armors which slow people more or less than others in their category are quite rare. It’s also worth keeping in mind that it is consistently weight category that we should consider, not sheer weight.
Unfortunately, blood biography combined with magical checkins and a spell-based binary search (probably using spirit planchets and generations of "retired" agents as spirits) to locate bodies spells doom rather cheaply as government spending goes.
Blood bio, cast with a drop of a ctreature's blood, gives answers to:
Who are you? (The name by which the creature is most commonly known)
What are you? (Gender, race, profession/role)
How was your blood shed? (Brief outline of the events that caused its wound, to the best of the victim's knowledge)
When was your blood shed?
Finding the corpse will have blood in its wounds, which then provides a "brief outline of events." It is reasonable to assume that a brief outline will discuss the method of attackers. Which then, (papers please!) will link them to the last internal checkpoint by their class descriptions or other characteristics linked to their identities.
To be clear though, the public side of things will be absolute silence. Because the public doesn't know about this appearance of weakness, there will be no advertising the weakness. (Otherwise people get the idea that harming the secret police is possible, and we just don't want that...) Reprisals are fine and all, but an aura of omnipotence is better. If the team missed any of its checkins or procedures, their supervisor (to the function of his ability to have fall-guys) will be tortured to encourage the others. If there are some rumors, some of the "usual suspects" will be rounded up and executed for a trumped up charge.
In terms of team notification, every team will, being lawful, likely follow "modernish" police practice of "check in with home base." The logistics of this vary, depending on infrastructure.
- Visible tech: A napoleonic semaphore is not out of the question, especially with items of "whispering wind." (Given how cheap this makes individual messages, combined with the efficiency gains from modern communications and the ability to spy on the communications of a populace, I see no reason why a lawful evil society wouldn't have one of these networks.)
- A wizard did it: Telepathic Bond may be made permanent. Every squad of agents should be placed in telepathic bond with their controller "back at base". Given the communications capabilities that this implies, it's the cheapest possible communications network. An "empire" (evil or not) lives and falls on its communications, which means that there should be a correspondingly high priority assigned to this. We can assert, however, that the idea of battle-ready flying squads ready to teleport to help requests may not be part of the repertoire, likely due to infighting and other politics. Still, even presuming that these aren't "always on" (maybe the controller is managing multiple squads) squads should check in when before they expect trouble and after they're clear.
The players get one missed checkin as a grace period, Then a "ministry of divination" (I'm assuming nation-state resources) steps in with a series of spirit planchettes and does a binary search to find the last location of the missing team (as a function of the region that they checked in from). The binary search only needs to be of a region the size that locate object (remember, both a corpse, the corpse's robes, and the identity documents marked with a specific arcane mark are all items) can cover. Happily, the players removed some of the evidence there, but a corpse is still an object.
That binary search takes exactly as long as you wish, as it's a function of the resources invested into the "ministry of divination"'s binary search capabilities and whether or not the "spirits in the area" are favourable to which side. Of course, if I was an lawful evil ministry of divination, I'd make sure that the spirits in the area were particularly well disposed to me: any spiirt that provides a useful answer has their family rewarded with a lowering of quota or other "random" bureaucratic positive outcome. Any spirit that obstructs this will a) have their family harmed, and b) be otherwise removed using normal mid-level adventurer capabilities.
If I was doing this in 3.5, I'd make sure that the communications infrasturcture all had the necrotic cysts implanted in them so that the parent-cyst could scry (and remote take over) any of her agents whenever she desired.
Best Answer
According to most scenarios, he wouldn't bother
(Edited commentary): A nature of the D&D game is that illusion and detection spells are in an arms race to reduce the prevalance of scry & die tactics. From a tactical point of view, the resources spent hiding a fortification are either better spent hiding something smaller but more secret or fortifying the same structure against expected enemy tactics. The lowest item cost is approximately a hundred thousand gold, and that's for a custom item that the DM may not allow. The only time when concealing a fortification makes sense is during its magical (don't bother if you actually have to hire people to construct it) construction in a barren wasteland/desert as part of the first stage of defences against an enemy able and willing to use armies. Rendering a castle hard-to-detect takes more than visible illusions.
The most effective anti-detection methodology is to not be there in the first place. Enchanting the ability to planeshift/teleport/fly into the structure is a necessary pre-requisite to hiding the structure, as without that enemies can rely on fairly simplistic means of kinetic detection. or the spell "Find the Path." As most structure-hiding spells are at 5th-6th level, find the path must be factored in as a potential threat.
Once the structure is enchanted to move (random-walk if possible, which is why the best method is some sort of planar travel), the first layer of detection-defense must be enchanting false vision into every part of the structure. Again, without considering metamagic cheese, a tower of london structure has a volume of approximately 1136340 cubic feet. (Not counting outer fortifications). Every casting of false vision consumes 268083 cubic feet, so 5 castings will be necessary to cover the entire structure. This will protect against trivial scrying, but not find the path.
The probable line of attack, given that the structure is on a random plane, is to use contact other plane or its equivalent to have an outsider answer "Is $location on $plane?" Repeat for a number of castings. Said outsiders may or may not know the answer, but given that the caster is contacting notable powers on the plane and that the structure may impinge on their domain, there's no reason why they wouldn't know the answer. Still, this forces the enemy to use non-trivial resources. However, neither screen nor false vision will prevent find the path from working. Happily, find the path will not provide a useful teleport target and false vision is sufficient to block simple scrying sensors sent upon the path. (As a note, obsucre object could block find the path... if it could be scaled up to cover a location. It would be worth doing original research so that obscure object is a cubic spell, rather than an object spell. Barring that, as that's a house rule, detect scrying might detect the find the path sensor, but probably wouldn't. Nondetection functions upon "object touched" and certainly prevents divination... but not without a chance of failure. It's worth enchanting it into the castle at an extremely high level. Private sanctum fails due to Find the path not being a scrying subschool.
Fundamentally, the only real protection against find the path is a fairly frequent random planar walk of the castle combined with a high caster-level nondetetion and implemented "false vision" spells.
That being completed, the logic below is valid.
(End edit)
There are a number of options here, depending on your budget.
The simplest method is to simply use Mirage Arcana enchanted into an item. At base caster level (not thinking about cheesing items here, there are rather large resources devoted to that act) a level 5 spell requires a level 11 casterlevel.
This provides for a surface area of 20 feet * 11, or 220 feet that needs to be renewed every 11 hours.
Looking at a fairly trivial example of the tower of london, a nice square keep.
Dimensions are here: roughly 110 feet per side
So 110x90 for surface area, or 9900 square feet per side. A casting provides a surface area of 220 square feet. Therefore, with this el-cheapo "put the spell inna stick" method, costing (as per here) command word activated, 11*5*1800, or 99000 gold, It will take a minion roughly 5 minutes per side to fully renew the enchantment. It's reasonable to have 4 watches and to have the captain of the watch renew the enchantment every watch.
Another option is the use of a bunch of scrolls of Permanent Image. Best incorporated into surrounding terrain, you can simply disguise your castle as a hill. While you'll want skills in some sort of artistic craft, creating a bunch of permed images of "portions of a hill" should function adequately to your purpose. The cheapest option (besides from spending a non-trivial amount of time casting it yourself) is with a spell-trigger item. At a 6th level spell, it can create image covering a surface area of 150 feet. To cover the 5 sides of the tower with believable "hill" coverings, you need to cast it 330 times, which means it's probably just more effective to put it in a command word activated stick. This has the benefit of not needing regular re-casting.
However, we're just getting started.
With a little more imagination, it should be possible to build the castle out of invisible stone. One gets invisible stone through judicious use of the "wall of stone" spell and the Invisible spell metamagic:
Notes: If the spell reasonably makes noise, has odor, or a tactile effect of some kind these effects are not hidden, it operates like any other invisibility effect. The “spell effects” refer to any magical manifestation of the spell, not indirect results of the spell. For instance, a ball of fire would be invisible but anything it ignites would be visibly burning.
As a sor-wis 5, spell, an invisible wall of stone is 8th level unless one employs typical tricks for reducing caster level of meta-magic. Still, this means that the fundamental infrastructure of the castle is invisible, reducing the problem to rendering the inhabitants invisible. A far more solvable problem.
Assuming one enchants a stick of permanency, a sor/wis 5 spell, at casterlevel 10 (it's more effective to do casterlevel 13 so you can make more things perminant) you can simply enchant a stick of invisiblity and render every stone and every item coming to the castle invisible, and grant all inhabitants a free see invisiblity.
A stick of permanancy costs... 5 gold per 1 XP on top of the base price, or roughly 340,000 gold for a stick at caster level 10. A worthwhile investment, however. The way to pay off the investement is to bring the minimum caster level to 12, so you can create endless walls of fire, for 608,000 gold and thereby dump functionally unlimited energy into the local civilization, with a concomitant increase in living standards.
There is, of course, the thoughtbottle option, but some things are too cheesy even to suggest.
All things being equal, the best way to hide a castle is to build it inside of the landscape and hide the bits that you changed with perm image. Beyond that, an item of mirage arcana and 4 shifts of guards should serve to hide the castle. The problem with this is that the castle is still vulnerable to scry&die and the most trivial examination of the local terrain (due to the natural layout of castles and their infrastructure (read: villages) ). While the infrastructure problem is also solvable, at a certain point it may make more sense for the castle to be flying (arms and equipment guide, probably, to which I don't have access right now, or the stronghold builder's guidebook).
Both of those books probably also detail additional building camouflage techniques, though of dubious utility.
Remember, when trying to hide a castle, you need to make sure it can hide against the expected threat. Make sure to perform a threat estimate before committing any gold, because most of these methodologies can be defeated by fairly trivial divination that a party of sufficient level to assault the castle will have access to.
Good luck :)