Situation: Level 4 Knight, 91 HP. Willpower low enough for a -2 save penalty (IIRC). A Crystal of Fireball is used, hitting my character, and killing her instantly.

The problem is that Fireball only does 1-1 + 4-12/level damage, so it should only do 49 damage maximum at level 4. So, how did it kill my Knight? Do items use fixed levels instead of scaling with the user's level?

One other test went like this:
After Fireball, my character has 17 HP left (so Fireball did 72 damage). I drank a Potion of Healing and it took me back up to 89 HP, giving me 72 points of recovery.

Problem: Heal only heals 1-15 + 1-5/level, so at level 4, it should heal a maximum of 35, but somehow it healed more than double that?

Clearly, the game isn't working as I am expecting it to.

By the way, I suspect that a Crystal of Force Wall may give more HP than a Mark of Force Wall. I think it may be time to do some more intensive checking of the game mechanics.

Slightly off-topic reply :-):

I just re-read this post the third or fourth time, and pondered whether or not I should reply to it, saying things you don't really want to hear, like: "Well, maybe it's a bug, but it doesn't look like one. Perhaps the stats of the effects of the fireball spell are affected by the circumstances of casting it in ways we don't understand."

Then an idea crossed my mind: Have you ever played one of the classic rogue-likes? Like Rogue itself, or Nethack or Angband or ADOM (some of them are still in active development and exist in a graphically more accessible form), etc.? With your interest in understanding the details of the game mechanics I could imagine that such games are a perfect playground for you.

I actually did figure it out: The Crystal of Fireball actually casts the spell at level 11 (regardless of your character's level), and the Potion of Healing at level 16.

The one problem with roguelikes, from this standpoint, is the permadeath mechanic. When testing things, it is much easier if I can save first and then go back to a previous save after performing the test; doing so saves a *lot* of time. For example, in this case I don't have to keep getting more money and managing inventory space for each test; I just load an old save before buying the item I was using for the test.

Incidentally, I *have* played a bit of Nethack, but it was mostly on wizard mode (which is basically the game's debug mode); while unsatisfying from someone who actually wants to be challenged by the game, it is fun if you just want to play around and test things. (One annoying thing: Getting the fake amulet via wish is annoying on wizard mode, as wishing for the amulet will actually get you the real one. Also, wizard mode isn't good for testing the normal limits of wishes, as they do not exist on wizard mode.)

Congratulations (for your solution of the fireball problem)! :-)

The permadeath problematic hits me, as a role-player, too. I don't like starting from scratch and repeating the same things again and again. I prefer immersive over interruptive gameplay.
But there is a simple solution: Exit (=save) the game, backup the save files or the whole game folder, and restore the backup if necessary. You can repeat this process as often as you like, have an unlimited number of backups if you want. Yes, it's slightly more cumbersome than an in-game saving / reloading option, but compared to the time you spend playing such a game and the fun you can have with it, it's acceptable - for me at least.
Yes, you may still have to replay a couple of minutes if you haven't created a backup immediately before something interesting happens, and yes, there is some randomness built in, which doesn't always let you repeat an encounter in exactly the same way. And purists may view it as violating the ethics and rules of roguelike gaming, as cheating. Fine with me - I'm playing for myself and not for others, and I'm not trying to impress others with my cheated results..
That said, I have to admit that I still haven't managed to complete one of those roguelike classics yet (mostly because I tend to lose concentration too soon, I guess).