The title couldn't be any more obvious in telegraphing that the final standalone Freescape title takes indeed place in a castle. But it is not any old castle - the place is possessed by an ancient force called Magister, who has a habit of turning anyone who lives in the castle into spirits, cursed to haunt its halls for eternity. The whole backstory is told by Magister himself, in form of a long form poem. It stretches over a dozen pages, frequently traversing from mystical, to threatening, to silly:

My name? Not now! it starts with M
Not Merlin , Mel or Male or Fem
Not Micky, Mao, select another
Not Mantovani, Mud or Mother
My title flashes into view
Before I've tolled my tail to you
I'm thirteen thousand years today
You are my birthday present, play!
And if you want to call me, cur
'Tis best you call me softly "Sir"

The hero only walks into this mess because their sibling has been spirited away into the castle by a giant monster bird. The previous games had alway remained ambiguous about the protagonist's gender, but here the player gets to choose whether to take the role of the Prince or the Princess. It doesn't make much of a difference, because the game is still played in first person, and there is only one obstacle where the prince can crouch underneath, but the princess has to carefully balance along the ledge around it.

All the player has to do is infiltrate the castle and find the room where the lost sibling is held captive. Of course this is not as simple as it sounds, as many of the doors in the castle are locked. Magister obviously didn't bother to employ a caretaker, and thus all the keys are scattered around the premises. There are ten keys to find, but also valuable treasures. (Why does the royal heir to a kingdom resort to looting an abandoned castle? State finances seem to be dire indeed...) Munching some centuries-old cheese surprisingly doesn't make the adventurer sick, but increases health and strength. There's also a bottle of strength potion, which cannot be picked up but allows seemingly infinite draws from it to heal up. Getting stamina up to Herculean strength even allows to do some heavy lifting at a few obstacles in the castle. The Rock Travel potion finally allows to teleport to any doorway you can throw a rock at - literally, once again.

For the first time in Freescape, Castle Master has a separate "action" button, raising the complexity a tiny bit, as some mechanisms have to be "shot" at - officially, the protagonist is throwing rocks - while most objects require to be interacted with at close range. Accidentally shooting a potion also destroy's the bottle, so all too trigger-happy players will get stuck eventually. The rocks are also used to deal with the spirits in the castle, which come in the form of bats, bedsheet ghosts and mice. The mice are especially vicious, as they often cannot be seen from any position, and the spirits start draining health as soon as the player enters their room. Killing ghosts is also essential in getting the Spirit Level up, which tips the odds in the player's favor for the final battle against the dragon.

Castle Master is quite a bit frindlier than the games that preceded it. Stupid mistakes like shooting the potion bottles notwithstanding, there are fewer ways to get stuck irredeemably, the strength potion makes players effectively invincible as long as they mind to return to it regularly, and the puzzles never get too far out there. (The way to get up on a roof is really fun, though.) Some hiding locations for the keys are crazy, like the one that is literally taped under the belly of a horse, but many others are lying in plain sight or hidden in typical places like wells or mouseholes. The building also seems much more intuitively structured than the confusing pyramid or the planetoid surfaces from the earlier games. There even can be found notice signs in some areas, which offer additional hints, in rhyme like the manual backstory.

The 16-bit versions of Castle Master are not simply ports, but completely remix the quest for a new challenge. The basic layout is the same, but areas connect differently, and there are quite a few new/replaced rooms. Many of the locations for the keys and locked doors are changed, and these versions actually introduce new ways to get stuck, including some pitfalls into the oubliette (a fancy way of saying "dungeon"), which equals an instant Game Over. Getting around in general has been made more difficult, as there are many blockades in the passages linked to switch puzzles, and a few doors that are bolted and can only be openend from one side. There's also an additional part to the quest that requires to find violet pentacle shapes.

The graphics have been improved quite a bit. After choosing the main character, the game shows an animation of the other sibling being grabbed by giant bird legs and flown to the castle. In the game, some rooms have added objects and are much more detailed than anything seen on the 8-bit computers, but they also tend to bring the engine down on its knees. The castle moat is populated by sharks(!) circling around the castle, and as usual the enemies gain the ability to float around in their rooms. The annoying houses have been replaced by flying birds, and you can find an ugly goblin named Xgor, who is much stronger than the regular spirits.

The IBM PC version this time got promoted to the same rank as the other 16-bit platforms, with mouse interface and all. It still doesn't support VGA graphics and only has PC Speaker sound, so it looks and sounds still inferior to the Amiga and Atari ST versions, but the opportunity to significantly speed up the gameplay (about 3000 CPU cycles in DOSBox are optimal) in combination with the mouse interface makes it the most playable version of them all. Since the original quest is more beginner friendly, patient players may want to try the Amstrad CPC version first. Only the Commodore 64 and Amiga get music this time, which is activated by default on both platforms because the visual cues when spirits attack are obvious enough to render the sound effects unnecessary.

Like Total Eclipse, Castle Master also got a sequel to be bundled with the original in later releases. It seems The Crypt received more love from its creators than The Sphinx Jinx, though, and thus it also made it onto 16-bit. It was also included in the Virtual Worlds compilation Domark released, which also contains Driller, Total Eclipse and the original Castle Master, but strangely omits Dark Side and, not so strangely, The Sphinx Jinx.

Following in the footsteps of The Sphinx Jinx, The Crypt doesn't offer much of a background story, and no choice of protagonist either. The goal is simply to escape from the six-storied crypt. This again means searching for the many keys while fighting off spirits - this time the bestiary includes floating furniture, jars and living cheese, alongside the familiar mice. These are present in all versions now, so the annoyingly tiny mice have to be hunted as moving targets on the 16-bit platforms. Even worse is another enemy that is little more than a haphazardly flying pixel. There are treasures to be found in the crypt, but most of them are lying in plain sight, so searching for them is not really part of the fun.

Thought I wouldn't look there, didya?

The puzzles are quite a bit meaner than in the first Castle Master, and since strengthening items are limited now, missing certain objectives in the beginning can result in a dead end much later, when there isn't enough cheese around to boost the protagonist to Herculean strength. Many puzzles involve an elevator that can be moved between the lower four stories, and the way everything connects between the multiple stories and across a ravine is very intriguing. The game may be a bit more easily frustrating than Castle Master, but figuring it all out feels all the more rewarding for it. A nice nod is a miniature of the castle from the previous game, which is even used to reprise a former puzzle in smaller scale. In the end the player gets to fight an impressive-looking, but actually kind of dumb three-headed Kerberos.

Incentive Software were always big on selling their design tools for hobbyists to create their own games in the same engines. Prior to 3D Construction Kit, the company published The Adventure Creator and The Graphic Adventure Creator for traditional parser based adventure games.

The 3D Construction Kit wasn't quite an all-purpose development tool, but pretty much rooted in the mechanics established by the Freescape games, first-person adventure games with a built-in shooting mechanic. At least it introduced support for strafing, a feature none of the previous games had. Within these confines, however, everything is heavily customizable, from creating 3D objects from scratch to designing the HUD and to scripting events.

The program breaks just about any law of modern interface design, and it's a major challenge to put together objects as intended, as the user kind of "walks" around the area in first-person, like in the games, and placing and moving objects is far removed from simple drag-and-drop. There's also no support for animations - the only way to implement them would be to put together several groups of shapes and move them individually, but at that complexity the engine would probably just surrender, as it already slows down to a crawl when a somewhat more complex object is on screen.

The software's major problem, however, was the fact that Incentive Software waited until they were done exploiting the Freescape engine with their own commercial games, and thus when it was released, the engine wasn't as groundbreaking anymore. Nonetheless the kit soon gathered a devout following in the UK, with its own fan zine, the 3D Construction Kit User Club Newsletter, and many homemade adventures, long before Doom became so famous for its modding community.

A year later, Freescape Software released a version 2.0, which brought several new features, like a sound effect editor, "transparent" surfaces by dithering, spheres (which due to the lack of shading look just like hovering circles) and cutscenes. Considering that at the time several commercial games supported textured environments, like Wolfenstein 3D and Ultima Underworld, these improvements couldn't save the engine from looking severely outdated, even though it still offered a much more thorough and honest 3D simulation than those American games with their 2D sprites and narrow corridoors.

Both major versions of the 3D Construction Kit also came with a sample game to demonstrate the features in a simple "collect X pieces of Y" quest. The first one has a space theme where the player collects gold bars for an alien in hope to launch a space shuttle. The second takes place in brown ruins, where the items to gather are candles, which are then shown being placed into alcoves and lit in cutscenes.