Talking about importing rules form one edition to another, I think that if I ever DM a Dark Sun setting on 2E, I will import the exhaustion rules from 5E. IMO would work better than normal
"dehydration rules". About our OSR game, I tried to run a one shot of ship of horrors. The lv 10 party died pretty quickly, they managed to figure out the reason of the horror on the ship, pick the required "stuff" on the bottom of the ocean, but when they reached the island, they triggered a trap and refused to let his companion to die and got surrounded by two snow golems + a couple of undead and died quickly... The module says that is a adventure for a lv 8~10 party. But monsters with 12 hit dices are not rare.
I prefer to not enter much on module details, but here is the stats of a Snow Golem - Ship of Horrors - Page 68
I think that if the party was a couple of levels higher. I played for months with the party and was expecting that they could at least reach the main dungeon of the island.
Note that the book uses descending AC. My group uses ascending, so 6 AC = 13 AC. The same AC of ring mail on mode modern editions. I even gave a scroll of transmute snow to stone to the magic user, expecting that he would use it against the ice golems which are common enemies, but he din't even memorized that spell.
Common thing to do for AD&D , 2E and OSR if i remember well is looking at HD , its rather simple (but not enough ) one HD per character level so here 12 roughly equivalent to a one level 12 character. A group of fully rested 4 levels 10 characters should handle 3-4 of those golems in theory. Now there's terrain and positioning, if they know the rules and combat mechanics. In this case obviously not ,if they get a scroll and dont get the clue to copy it on the spellbook.
Here's some guidelines i found , rules cyclopedia :
1. Figure out the party level. Do this by simply adding together all the levels each character has.
If a character is wounded, treat it as being at least one level less than their actual level.To determine what their effective level is, do the following:
If the character has taken damage equal to their level, count them as being one level less than actual. For example, a 4th level character that has taken 4 points of damage would be counted as being effectively 3rd level (reduced by 1 level).
If a character has taken up to double their level in damage, then reduce their effective level by 2. For example, a 10th level character that's taken up to 20 points of damage would be considered as being effectively 8th level.
A character may not have their effective level reduced by more than half due to damage.
2. Determine the Monster(s) Adjusted HD value.
2a.Start with the actual base HD.
If there are additional hit points added to the HD, divide the additional hit points by 5, round up, and add it to the base HD. For example, if a monster is listed as having Hit Dice 10 + 7, you would divide the + 7 by 5 (1.4), round up (2) and add it back to the base (10) for a total of 12.
2b. If there are subtractions to the HD, subtract 1/2 (half) a HD for each -2 [default seems to be to round down unless explicitly told otherwise]. For example, if a monster is listed as having HD 10 -7, you would subtract 1.5 HD (the extra hit point left over is lost) from the base HD (10) for a total of 8.5.
2c. Special Abilities
For each special ability a creature (or NPC) has, divide their base HD by 2 and add that number to the Adjusted HD. For example, if a creature is listed as having HD 10 + 7, and two special abilities, you would divide the base HD (10) in half (5) and then add it back to the base twice (since it has 2 special abilities).
This means that your HD 10 + 7 creature with two special abilities winds up with a total adjusted HD value of 22.
If the NPC (creature) has +2 magic weapons (or their equivalent), this also counts as a special ability, and modifies the HD value as already explained.
2d. Spell casting
If an NPC (creature) can cast spells, take the highest level spell that can be cast, divide by 2, and then divide the resulting number by the number of NPCs (creatures) in the group. For example, if you have 2 NPCs and one of them can cast 6th levels spells, you would divide that by 2 (3), and then divide the result (3) by 2 again (since there's 2 NPCs) for a total adjustment of 1.5 HD.
If both NPCs were listed as being HD 10+7, had 2 special abilities, and one of them could also cast 6th level spells, their total adusted HD value would be 45.5
3. Determine the challenge
Divide the Adjusted HD value by the party level. As a rough guide for what the percentages work out as, here's the suggestions from the RC:
Less than 10%: Too easy. Play it for laughs, ignore it, whatever. Only if the party is injured or weaponless is it really worth considering.
10%-20%: Minor. Random encounters should be around this difficult.
20%-30%: Distraction. It'll cost the party some, but isn't especially challenging on it's own. Best to use this level if you want a constant stream of combats with little chance for the part to rest up and recover.
30%-40%: Good Fight. This can be a tough random encounter, or a fight lasting about half the adventure session.
50%-70%: Challenging. The party will definitely hurt, but the odds are still in their favor if they're smart. About 3 to 5 of these for a dungeon, depending on the size of the dungeon/length of the adventure.
70%-90%: Major. This is usually the main showdown of an adventure/dungeon.
90%-110%: Risky. Chance of party members dying is high. This is mostly suitable as a "cap" for the final encounter with the Big Bad Evil after a series of adventures leading up to him/her/it.
110%+: Extremely Dangerous. This is basically impossible for PCs to win.
So here we go "Divide the Adjusted HD value by the party level" 90%-110 risky in your case
