Possible spoilers ahead, looking for help from game veterans:


So, I was exploring the pyramid in the NE of the map, by castle Dragontooth, and all was going dandy. I got 3 Ultimate Power Orbs and the crystals on the left game me vital hints, so great, right?
Well... The crystals on the right... they age my characters. I didn't know this. I only found out after SAVING my game with my characters at the ripe and natural age of... 78. Wow, huge issue, but I can just go to the Fountain, right?
No, the Fountain of Youth has done nothing. Is there any way I can get back my stats, and reduce my natural age of 78? It was be a huuuge downer if this ruins my entire game.

Without cheating, unfortunately no, as the orbs actually cause a year of in-game time to pass. This would also put you closer to running out of time to complete the game, provided that the game's time limit had actually been correctly implemented. (There apparently is an "out of time" message in the game's code, but the time limit is not actually implemented, or if it is, it doesn't actually work.)

On the other hand, if you are willing to cheat, you can open your save in a hex editor (remember to back up your save first), figure out where the year is stored, and hex edit it back 60 years; this will restore your age and fix your stats.

One thing to note: Don't set the year back *too* far; characters who are younger than 18 suffer penalties, which (IIRC) become increasingly severe as the character's age approaches 0. (Yes, they did implement this, even though such ages never come up in normal gameplay.)

Another thing you could try if you *really* don't want to cheat, but still insist on fixing your age (and I don't know if it will work): Keep hitting the crystals until your character's age would be 274. If the programmers didn't check for integer overflow with your age, then this will cause your character's age to overflow and become small.

And here I thought I was in a pickle when I pissed off a bunch of liches and got my entire party to 125 unnatural age, prompting every party members to instantly die whenever a new day started. The pickle you are in is definitively a new one for me. I hope you'll manage to get out of this one.

Actually, in MM3-5, age doesn't directly cause death; you only risk death if a stat is reduced to 0. This has actually led me to develop an interesting strategy for World of Xeen: Use the stat boosts that boost every stat at once on the Cleric so that none of her stats risk reaching 0 at old age, then use Divine Intervention as the primary form of healing.

Okay well age caps out at 254, so it looks like editing the save file is my only option. I'm not really sure how to do this, but I am trying it now, I'll let you all know how it goes.

How high/low is the stat bonus/penalty ? Do your characters die when resting even if all stats are all >0 ?
It shouldn't be too difficult to keep all stats above 0, 10 points more or less don't matter much near the end considering it takes 25 attribute points for +1 when above 50.
Since they're only 78 years old you have more than 1 year before they get 80, much longer than needed to finish the game.

Another method to finish the game normally is creating a new party which should be able to catch up quickly using the equipment and money you have in combination with the knowledge you gained (XP can be gained with arena fights and for all stats except speed can be raised without limit).

I second this. The game is easily finishable (with careful saving), so consider just playing onward so you can say you finished it without "cheating".

In my case, the entire party just kept on dying at 5AM or whenever I slept due to old age. I had to hike all the way back to a town, hire a young hireling like Allan Bow or Sir Gallant whose sole job was to be alive and able to revive the other party members at the temple every morning. I had to check a walkthrough to find where the fountain of youth was hidden and punch my way there.

After that episode, whenever people asked me which Might and Magic game was the best to get into the series, I always suggested either Might and Magic VI or World of Xeen because these games don't have that issue with magical aging, either it's not a problem or the way to remove magical aging in those games isn't hidden way deep into a dungeon. In my case I was rather lucky I was able to backtrack to a town and hire someone. I could have very easily saved in a spot where backtracking to a town in a timely manner could have become an impossible task.

Also 1 year in MM III is much smaller than 1 year in World of Xeen, and 1 year in World of Xeen is much smaller than 1 year in MM VI+.

MM IX removed age entirely - one of the few things MM IX did right.

Also, in MM6+, unless you're completely not paying attention and it accumulates a lot, the unnatural aging is in very small increments. Usually you won't get within the dying range, unless you screw up big time.

...you can die of old age in MM6+?

Learn something new every day!

Not really since Mr.Wizard teleports you instantly back to Fountain Head when you call him for help.

Still at a stand-still. I don't know if I have it in me to restart totally, and creating a new party would make them miss out on items and stat boosts that I already redeemed. Idk, maybe it wouldn't take that long to catch up, I still have a strong craving for some Might and Magic.
I just feel a little bit betrayed by the game haha. Kind of a similar feeling I get when I die in a very successful game of NetHack. I had a ton of fun though, maybe I'll just dive in and restart, I just don't have that much time to play when school starts up again.

Oh, I forgot to mention that most of my characters, all except my Barbarian, die when I rest and so I don't really feel like I want to spend the rest of the game trying to keep everyone alive- I'd rather restart.

You might lose out on some stat boosts, but if I understand things correctly, you can just swap all the items and equipment to the newbies. Maybe only generate half the newbies at a time, moving everything to keepers while making them.

Developing a strategy to improve the new characters effectively can be a fun challenge.