[RPG] How to appropriately scale the DC for the Madness Effect from the Sunken Asylum adventure for Pathfinder when converting it to D&D 5e


I'm a D&D 5e system GM who runs a West Marches style campaign where I run a session a week with all sorts of adventures. This means I borrow a lot from the internet and quite often take monsters from other systems and convert them.

I generally have a good feel for what I want the encounter to be, and make any conversions generally match the difficulty I'm after. Sometimes however it might be nice to run monsters/encounters as they were originally designed (if this is even possible)

I have recently been looking at this Pathfinder asylum adventure which inludes the following "Madness Effect", summised:

While in a visual patch of madness all light begins to strobe at irregular intervals. This strobing also affects darkvision. When the strobing starts, each PC needs to make a DC 24 Will Save or suffer a −8 penalty to Perception checks, and a −4 penalty to all other actions. A successful save reduces this penalty to −4 and −2. Additionally, concentration checks must be made to cast spells successfully (DC 15 + spell level × 2). During combat, a DC 15 Perception check must be made to target an enemy, otherwise, the enemy appears to not be there when the attack is made, or if there is a friend within 5 feet of the intended target, that PC is targeted by the attack instead.

I would normally take the Will Save and penalties to Perception checks and just make the an appropriate scale in my campaign. These however seem really high, which makes me think that Pathfinder skills go up way higher than D&D 5e, either that or these are really difficult effects to save against, or maybe a combination of the two.

My question after the relevant rambling is: Is there any relationship between these Pathfinder difficulty classes and D&D 5e difficulty classes?

Best Answer

Pathfinder characters usually add a number equal to three plus their level to skills with which they are trained, or "proficient" in D&D 5e terms. A D&D 5e character gains a much smaller proficiency bonus that maxes out as +6 at 20th level.

When converting between the two, remember that D&D 5e made two major design evolutions over its predecessor, D&D 3.5, which Pathfinder is heavily based on:

  1. D&D 5e now uses bounded accuracy. In short, numbers are much smaller, and you'll almost never see something like a DC 24 Wisdom Save. The CR 24 ancient Red Dragon's breath weapon is DC 24.
  2. D&D 5e simplifies the bonuses and penalties of D&D 3.5/Pathfinder to a simple system of Advantage/Disadvantage. It was felt that the extra complexity of counting small numbers detracted from the gameplay more than it helped. You won't often see penalties to Perception checks, but instead Disadvantage on Perception checks.

As a result, you will never see anything as complex as the quoted text as an area effect in D&D 5th edition. How this might work in 5e is simply as follows:

While in the area of strobing light, all creatures have disadvantage on attack rolls and Wisdom (Perception) checks. Creatures which do not rely on sight are immune to this effect.

The D&D 5e Dungeon Master's Guide, p, 230 gives excellent guidelines for setting a DC for a saving throw or skill check. Ask yourself whether this check should be Easy (10), Moderate (15) or Hard (20).

The rules on Advantage/Disadvantage (DMG p.239) suggest that this situation is one where that applies (emphasis mine):

Consider imposing disadvantage when...

  • Circumstances hinder success in some way.
  • Some aspect of the environment makes success less likely (assuming that aspect doesn't already impose a penalty on the roll being made)

Note that imposing a skill penalty and allowing a saving throw against the effect are still valid mechanics in D&D 5e, but in general, these are much simplified to use the Advantage/Disadvantage system.