This is a subject that I have been mulling over since I released Hearkenwold for FRUA last year. One of the more questionable design decisions I made was to bump up the magic resistance of certain enemies in the monster editor. I'd like to go through the process about why I took this step, and get feedback whether it is worth re-visiting and adjusting the numbers.
First, I left low level goblins alone, so they still have the default 0 for their magic resistance. But when I introduced a goblin "chief" in one of the starting areas, I was a bit dismayed that a 1st level magic-user could ensnare him in a sleep spell and thus render the enemy a one-hit kill. This was supposed to a creature to at least give level one characters some pause. So I went into the editor, and bumped up the MR to 25.
Suddenly, more often then not, this goblin chief will resist a sleep spell, requiring the party to work harder to take him down.
As I continued to build, I would classify the monsters by type or level, ranging from 1 to 4. So essentially, I started giving 2nd level creatures 20% magic resistance, 3rd level creatures 30, and 4th level monsters a 40 MR. I never approached the levels of drow or rakshasa. Again, the whole reason I increased from 0 at all was to avoid these enemies easily being disabled by sleep or stinking cloud. Below is a tougher version of a bugbear, a Bugbear Lord, and its adjusted MR:
The way I figured, even with as much as 40% magic resistance, a monster should still fail saving throws half the time? As it turns out, I think player magic-users probably saw their spells go off to no effect, more than they would like. However, I tested this module from beginning to end, and did see some of those higher MR monsters go nauseous or held, from time to time. I thought it added an element of unpredictability to the battle.
One memorable encounter for me when I was testing, had to do with three minor demons. These were tough opponents even for characters who were 3rd or 4th level. I found it crucial to be able to take at least one of them out through incapacitation, in order to be victorious. I watched magic-user or cleric spells fail to work numerous time, until it actually rendered a status effect on a demon. That changed the tide of battle. As a player, I thought that was an exciting moment. And it would not have been the same if you could depend on putting monsters to sleep, or held, or caught in a stinking cloud every single time.
Another point I would bring up, unlike the traditional Gold Box adventures, Hearkenwold does not have massive scale battles. At most, I think the largest enemy group was 10, and even outnumbering the party 8 to 6 was not too frequent. More often the case was the party going against smaller, concentrated numbers of challenging opponents, at least in theory. I think the reason sleep was so powerful in the Gold Box games, was because the player could often face hordes of monsters, and taking out as many as possible was a necessary tactic. With this module's smaller skirmishes, suddenly, helpless foes could make an intended dramatic battle more of a cakewalk.
Nevertheless, after release, I wonder if I should scale back the magic resistance. Maybe 40 or even 30 is too much. I do not know the actual percentage mechanics under the engine, or if the dice are loaded in favor of the monsters. Perhaps just 20 or 25 MR, would be enough to make those tougher enemies resistant without rendering player mages ineffectual.
It's an area I would be interested to hear from designers and players.