Bandit Mook: The Smirking Sneak Thief can steal your money or whatever's on your belt, then randomly teleport to anywhere else in the level (including hidden rooms). Very agile and requires three fireballs' worth of damage to kill. You can get your stuff back if you can find and kill it.
Cast from Hit Points: The player is allowed to keep casting spells after running out of mana by drawing on their own constitution, (rapidly) lowering their max HP (and turning their mana level negative) until the player suddenly dies. This can be exploited in a Good Bad Bug, though.
Chosen One: You, for some reason. Probably a descendant of a king or something.
At the end of Part One, your dead father comes before you after touching your hallucinogenic family heirloom to tell you it is up to you to unseat the higher evils.
Specifically, you are the true heir of the Castle of the Winds, your father being the last survivor of the massacre and depositing you in your small village as he lay dying, the amulet being the key both to your identity and entrance to said castle.
The Dev Team Thinks of Everything: Using Save Scumming, one can identify cursed items, then reload and sell those "unidentified" items to the unknowing shopkeeper for a lot of copper. But you can only do this so many times. Do it too much and the shopkeeper will refuse to buy unidentified items from you anymore, demanding you get them identified first.
Doomed Hometown: Triggered by either deliberately reading or leaving the beginning mines with the parchment found at the bottom, which when read is discovered to be the Big Bad's orders.
Which also provides a jarring Gameplay and story segregation moment. If you drop the parchment just before the exit of the dungeon, you can exit and visit the still intact town as normal. As soon as you return to the dungeon and either read the parchment or exit with it (which triggers the autoread) the town is instantly destroyed, even if you immediately turn around and come back.
Dummied Out: There are a bunch of weapon and armour enchantments that are never seen in game, even though they appear to work just fine. The only way to get them is by hacking a save file.
Hot Bar: You get 10 buttons at the top of the window to set commonly used spells to. Unfortunately, 12 of them are frequently useful. Have fun! (Of course, you can always access any spell through the spell book, but that takes longer)
Human Sacrifice: There is a prisoner for the player to rescue from this fate. Once you first hear his screams, you have a limited amount of time to clear out all of the enemies in the sacrifice room and untie him. Don't try and untie him if there are still monsters in the room, however!
In-Universe Game Clock: The game keeps track of time for you. Unfortunately, the only things it's used for in the final version is for when stores restock their inventory, and there's a small number of magic items that have a spell they can cast once per day.
Mirror Match: Shadows and Shades appear as transparent versions of the default male player character. However, it's only the monster's appearance, as it uses the default AI. And, the effect is lost if playing as female (or, with a custom icon).
Old Save Bonus: Activating the pendant found at the end of the shareware game for the second time allows you to create a save that can be loaded in the second part, allowing your character to continue exactly as you left it. Not so much a bonus, though, as a necessity, as the game is designed with a high-leveled character in mind. The second part does spot you some levels and equipment if you start from scratch, but such a character is still at a significant disadvantage.
Orphan's Plot Trinket: An amulet belonging to the protagonist's biological father. Recovering it is the goal of the first game.
Our Dragons Are Different: Four elements of dragons (fire, lightning, ice, and poison). Older dragons are stronger, with "Ancient" dragons being the most powerful.
Palette Swap: Many enemies share graphics. Sometimes they're recoloured, sometimes not. Related species tend to have similar graphics, though.
Power Glows: Enchanted items are generally depicted as having a blue aura. On the other hand, cursed items have a red aura...
Purely Aesthetic Gender: The only effect of the gender is which icon you have. And, if you use a custom icon, it's totally irrelevant.
Rare Candy: Draughts of Increase Strength and so forth for each stat and whole level, as well as cursed counterparts that permanently do the opposite!
Save Scumming: Combine with the Detect Objects spell and reload after first entering a new dungeon level until you get a favorable selection of items, like Books of Spells. You can also use this to feed shops unidentified cursed items, but it's not really worth the trouble. Also useful for identifying uncursed items for sale and use at the beginning of the game, before the Identify spell is acquired.
You CAN sell unidentified cursed items at the shop, but only so many times. Do it too much and the shop will refuse to buy it, telling you "You've sold us too much worthless junk already. Get it identified first!"
Scripted Event: Although most of the dungeon floors are randomly generated, certain rooms are guaranteed to show up in certain places, and certain enemies are guaranteed to drop plot-relevant items.
Shareware: The first game was shareware, while the second one was commercial. Eventually, the creator released both versions as free ware.
The Undead: Zombies, Skeletons, Wraiths, Ghosts, Shades, Vampires; you name it, it's got it.
Unidentified Items: The game has the Identify spell as a single-use scroll, multiple-use staff, or (permanent) spellbook. Each town also has a sage that can identify items for a fee. Equipment may be enchanted or cursed, and magic items like potions, scrolls, and wands are completely unknown until you dare to use them or use one of the identification methods.
Vendor Trash: Virtually every type of equipment has a broken or otherwise useless form — from broken daggers and ripped cloaks to rings of adornment and dead wands. You don't need to carry around flasks of water because there's no thirst meter to watch, and you can't write anything onto blank scrolls.
We Buy Anything: Averted. Shopkeepers will generally only buy items that they can sell (and promptly puts them up for sale). The Junk Shop will buy anything (and is the only one to accept cursed and broken items)... but only for a paltry 25 copper pieces or less; sold items disappear for good. However, other shops will still accept unidentified items that the player (through Save Scumming) might know are actually cursed... up to a point. Sell a shopkeeper enough actually-cursed items and they will refuse to accept unidentified items anymore.
With This Herring: Somewhat averted. The local ruler in the final town won't believe you're The Chosen One or give you the time of day until you've proven your worth in the dungeon. At certain levels of progress, though, he gives you an item or some cash, but what items he does give you aren't all that impressive. Regardless, the shops are more than willing to charge full price for all your needs.