No, I am NOT done talking about intelligent weapons! While this does seem to be the topic that I can't stop writing about, we are almost done, I swear!
To sum up - according the the AD&D DMG intelligent swords are much more common than I thought (and based on comments, much more common than anyone seems to play), most of them are Good, and a lot of them talk. There seem to be good reasons for fighters to use intelligent weapons and equally good reasons for magic-users to not use intelligent items. And, the topic of today's discussion -
Virtually anything can have an enchanted intelligence.
The DMG specifically mentions archways, door, buckets, pools of water, fire, illusions, and more.
When I was discussing this with my sons they alternated between stunned amazement and cackling with glee. Both reactions were about the sheer gobsmacking possibilities. Their initial ideas (in the order they gave them to me):
My oldest: "What if there is an earthquake and a magical pool drains into a river that is also diverted? A village could be flooded by an intelligent river that likes its new home!"
My fourth: "What if the fire that threatens the mill is a Lawful Good fire forced to burn buildings to survive? It can Heal people once a month but needs timber from a family's home to survive."
My second: "Imagine this - a man comes to the party asking them to break the curse that plagues him. The party learns that he is an intelligent illusion that thinks he's a real man."
My third: "The entrance to the cathedral is an intelligent archway that can Know Alignment on all who pass through and will tell people that they need to Atone."
And my first blush: "A wizard's tower with an intelligent door that can speak, knows the password, and can cast Wall of Force - the door man is the door!"
In many of these cases the intelligent item will not have routine contact with a creator or wielder that could lead to a personality conflict, making these sorts of items much less dangerous for clerics and (especially) magic-users to make and use. Because of the costs we also can assume that the vast majority of these items would be made by demi-humans and clerics with the fraction made by magic-users both very small (probably 10% of the total at the very most) and the most powerful.
I will let you and your imagination think of more amazing things you could do with autonomous intelligent items with magical powers!
But this means that my discussion of types of intelligence in magical items might need to grow. The fifth category will need to be "true intelligence created solely by magic". This would be much more than a types of 'expert program of magic' that uses if, then statements to mimic intelligence, but a much closer approximation of actual intelligence with some autonomy and free will, and even its own knowledge unique to itself.
This is at least implied by the spell Unseen Servant and its 'cousins'. An unseen servant is explicitly not a creature of any sort, but is a 'force'. This force can obey orders, such as 'open that drawer' but also can do things like clean and mend even if the caster doesn't know how to mend. And other spells point to similar autonomous skills and at least some level of reason - if we expand our attention to spells that are not in the core 1e books but were in modules and such we see things similar to an unseen servant that can cook, mend, make camps, hide tracks, etc.
It isn't hard to imagine a powerful mage creating a new intelligence whole cloth for a powerful item, is it?
But let's also think about what a world like a fantasy RPG is like from a new angle for just a few moments.
In science fiction one of the most popular themes is First Contact, the initial encounter of Mankind with other sentient creatures. Many of these stories are classic books, movies, or TV; The War of the Worlds, First Men in the Moon, A Message from Space, Contact, A for Andromeda, E.T., His Master's Voice, Close Encounters of the Third Kind, and a lot more.
One consistent theme is - how would we understand a different sentient being? How much of how we think and communicate has to do with what we are physically and how much is as abstract as the idea of consciousness?
Many fantasy worlds have a lot of intelligent creatures in them that aren't human. AD&D is like that - there are a lot of intelligent non-humans.
A rather shockingly large amount, actually.
And sure, we can argue that while elves, dwarves, orc, goblins, halflings, gnomes, goblins, kobolds, hobgoblins, hill giants, ogres, etc., etc. are, well, just 'humans that look funny' as far as the nature of their intelligence is concerned, we have some much more extreme examples.
Mind flayers are lovecraftian horrors that communicate via telepathy and prey upon intelligent creatures; beholders make mind flayers look like a favorite cousin! We also have ropers, neo-otyughs, aboleth, boggart, etc., who are very inhuman in everything from appearance to senses to lifespan to diet.
If you ponder 'how different must elves be from humans since elves live so very long?' try pondering how much different a dragon must be, or a foo lion, or a xorn, or a slithering tracker!
Stanislaw Lem, perhaps the most widely-read science fiction writer fo the 20th Century, is justly famed for his book Solaris. Of course, one of the central themes of Solaris, and a number of Lem's other works, is the impossibility of two radically different types of creatures communicating even when both are highly intelligent.
We can assume that the majority of intelligent humanoids in an RPG are close enough to communicate at least a fair amount (and I wonder if the grouping of 'demi-human' versus 'humanoid' is as much about communications and sympatico types of sentience as about alignment). But we also know, directly, that there are intelligences that fit into Lem's category. Cloakers are said to be so "other" that while demonstrably intelligent no intelligent communication is possible with them.
So we know that 'totally alien intelligences beyond the possibility of communication' exist and are 'canonical'.
Think of the possibilities in world building alone! What if the Elf-Dwarf conflict is innate to their comprehension of reality because of their modality of sentience? As mentioned, what if orcs, goblins, etc. are innately evil not due to a curse but because of the very nature of their intelligence - the fact of their sentience makes them hate creatures not like themselves? Imagine nations facing each other across an ocean where not only is communication between the nations very difficult because they have radically different emotions but also the aquatic race in the ocean between can't communicate with either nation at all?
So let's get back to intelligent items. We know that residual magic can cause gret changes in the environment so that inanimate objects resemble living creatures and have at least a rudimentary intelligence (mud men, remember?). And we also know that intelligent objects are possible and varied.
Imagine this - a wizard has a compound on the shore of a small lake. He has boats which are enchanted to move on their own; the stones of the quay were quarried by magical servants; The nearby arch was enchanted to sense the intentions of those who passed through it; friendly nixie live in the small lake; decades of residue of alchemy wash into the water. Then, tragedy! There is an attack and the mage and his servants all die with the powerful (but unintelligent) magical sword of his gurad captain falling into the water.
Over the decades the compound falls into ruins: the boats rot away, the magical wood drifting into the lake bed; the arch collapses, its enchanted stones being worn away by the water alongside the magically-quarried stones; the magical sword corrodes into rust that mixes with the ashes of burned spellbooks that washed into the lake as they settle upon the corpses of the long-dead nixies who perished in the fight.
A willow which first sprouted long years after the fight grows upon the shore of this small lake, its roots knotted along the bank and its withies dipping into the water. It takes many years but the willow begins to 'awaken', to sense its surroundings, and to think. It takes more long decades, but eventually the willow is, on its own, intelligent.
Can it communicate? Could humans or dwarves understand it? Can it speak? Listen?
And more importantly in the overall picture, imagine a world where this can happen, the impact this would have on life! Do foresters talk to trees before they cut them down not out of quaint folkways but rather because the tree might actually answer them? Could that brooch passed from mother to daughter for generations as part of bridal gifts actually tell you about the family's history? Might that cart horse actually be, yes, smarter that the teamster - and the teamster is pretty smart?!
As above, I leave the rest to you. But the next time you roll for random treasure...
...don't forget to check to see if it is intelligent.