As we get deeper into adventure game history, it is harder to pick out “notable firsts”, but I think Castle of Darkness has to qualify on some level. It is the first adventure to make extensive use of animation and the first the graphically represent the player character from a third-person perspective; in other words, a direct predecessor of the entire “point-and-click” genre.
From the Gallery of Undiscovered Entities.
It is the only game by Michael Cashen, and the only product published by The Logical Choice, a store chain in Baltimore. Quoting Michael himself:
Like a lot of small computer stores, back in those days, The Logical Choice had a meeting room where we fanatics gathered and discussed various problems. A big topic was how to maximize memory (64K RAM was huge then) and I figured out how to tap into the Apple II’s graphics in ways I could get a lot of bang for the byte. Castles of Darkness grew out of those methods since I could now fit a lot of information on a 5″ floppy disk. George, the owner of The Logical Choice, contracted to publish it and had to talk me out of writing a cassette version: I felt sorry for the many who had not yet graduated to floppy disks (most owners of the first Apple II’s transferred information with a standard audio cassette – and my Apple II Plus was one of the first: it had the serial number 00109).
This is “castles” plural, so you start out in front of two of them, here to break “the curse of the Evil Wizard Grimnacht”, who has plunged the world into perpetual night and captured a princess.
IT IS OUR HOPE THAT YOU, BRAVE SOUL, WILL FIND THE WAY TO END HIS CURSE.
While all action is viewed from a far third-person perspective, the game is not free-roaming; you still put in parser commands, and the character animates when moving around or fighting enemies. A sample:
A pickax is the only helpful item to start; on the far east you can DIG ROCKS to find a secret passage (this took about fifteen minutes of noodling to find). Inside there is an orc; combat is just a matter of KILL ORC over and over, but the animation makes the game feel slightly lively about it. I then got stuck until realizing the interface concept here: you need to often refer to directions. FEEL NORTH reveals a secret exit, and OPEN NORTH is the way to open it. (I quit in frustration at an early play-through by trying to OPEN DOOR.)
The need to feel for secret walls is extensive enough this feels slightly RPG-ish.
Also interesting is the graphical conceit: rather than each location being custom, like in the On-Line Systems games, there are a set of “standard” graphics that get mixed and matched. A sample, so you can see the re-use.
I found a charm with the message 5-26-13-18-8-19-4-12-9-16-8-18-13-12-13-22-9-12-12-14. The numbers (when matched to the alphabet backwards) spell out VANISH WORKS IN ONE ROOM. This was useful when I encountered a wraith.
Typing SAY VANISH causes the wraith to poof. I’ve also encountered a troll which I can’t put a dent in (although he’s not blocking anything, so maybe you’re just supposed to avoid him), some locked doors and a locked chest, and a key I can’t reach.
The game mentions 78 indoor rooms, and I’ve got 19, so I’m about a quarter of the way in.
Renga in Blue 
This kind of mixture between graphic”point-and-click” adventures and interactive fiction is really interesting, even more when I realized it was written in 1981. Wow!!
In 1983 there’s another of this kind called Valhalla, for Spectrum.
I’m a little fond of this kind not because there are good examples of this format, but because in Spanish we have a really nice amateur adventure in the nineties, called Barbarian Quest.
Fantasy (which I’ve referenced once) was Level 9’s first game, and is from 1981. Pete Austin described it as “like Valhalla but without graphics”. I might try Valhalla a little early just so I can write a post about Fantasy, which is currently a “lost game”.