I'll be the DM for a new campaign and I don't particularly like how Impervious was handled in this edition. But, I also think that the 2nd edition one was OP (overpowered). The idea behind the solution is to make the defence with impervious less likely to be damaged by an attack, but still has a chance to damage it with a "lucky" shot.

(note: Since Penetrating is the counterpart of Impervious, it did little sense to me to divide this question into two questions.)

I added, in italics, the following.


Any effect with a resistance difficulty modifier equal to or less than half the Impervious rank (rounded up) has no effect. Furthermore, if the resistance difficulty modifier is equal or less than the impervious rank, the defence roll has advantage (roll two d20 and take the highest). The ranks in impervious cannot surpass the ranks in the the defence that it affects.

For example, if a resistance difficulty modifier is 9 and the impervious rank is 10, the defence roll would have advantage.


...the target must make a resistance check against an effect rank equal to your Penetrating rank. The defence check against an attack with Penetrating is made normally (without advantage) if the ranks in Penetrating are at least half the ranks than the Impervious ranks (rounded up).

Example, an attack 10 with penetrating 5 would ignore the advantage of a defence with impervious 10 but not of one with 11. Moreover, an attack 4 with Penetrating 4 will force a defence save with advantage against 4 damage.

Are these changes to impervious and penetrating OP?

  • \$\begingroup\$ Advantage is a defined mechanic - the feat-like abilities bought for 1 build point. How is that related to a resistance check? \$\endgroup\$
    – ValhallaGH
    Commented Dec 3, 2019 at 21:54
  • \$\begingroup\$ @ValhallaGH The relevant information of what an advantage in this question means is in the parenthesis that followed the first reference of it. It is a term that was popularize by d&d 5e. I may change a bit later its name if that make it clearer. \$\endgroup\$
    – Chepelink
    Commented Dec 4, 2019 at 13:29
  • \$\begingroup\$ I marked this one to close as being Opinion-based since there really is no basis for "overpowered" since it's simply halfway between 3E and 2E Impervious. \$\endgroup\$ Commented Dec 4, 2019 at 14:31
  • \$\begingroup\$ @SeanDuggan Correct me if I'm wrong, but I've read several times (and agree with) that the Impervious of 2e is considered OP, while the 3e version of it is UP. Is not that an actual argument that can be used as a part of an answer, followed by an analysis of that middle point? And secondly, would it be better if the question is "is this change balanced"? \$\endgroup\$
    – Chepelink
    Commented Dec 5, 2019 at 0:51
  • \$\begingroup\$ @Chepelink: I could post an answer showing that your results will fall in between the two values, but that doesn't really answer the question of whether it's "overpowered". Or if you want to change your question to how it would work relative to the two systems, I could do that. \$\endgroup\$ Commented Dec 5, 2019 at 1:11

2 Answers 2


This change could make Toughness-shifting even more powerful

It's a fairly well-known fact that, for a straight slugfest, a Toughness shift of about +3 is statistically ideal, and that there's no real benefit to being defense-shifted (ditto for damage/attack bonus shifts, as they effectively cause your target's shift). Assuming PL 10, this is going to further exacerbate this difference. For example, for a PL 10 non-shifted defender defending normally against Damage bonuses from +5 to +10 for Impervious, their chance of avoiding any damage are the following:

  • +11: 25%
  • +10: 30%
  • +9: 35%
  • +8: 40%
  • +7: 45%
  • +6: 50%
  • +5: 100%

With your Impervious change, this becomes

  • +11: 25%
  • +10: 51%
  • +9: 57.5%
  • +8: 64%
  • +7: 69.75%
  • +6: 75%
  • +5: 100%

Whether this is "over-powered" depends on your point of view. In 2E, everything from +5 to +9 would have been at 100%. I'm just noting that this makes Toughness/Damage shifting even more advantageous.

  • \$\begingroup\$ Could you define what you mean by “toughness shifted”? \$\endgroup\$
    – fectin
    Commented Dec 6, 2019 at 17:17
  • 1
    \$\begingroup\$ @fectin-freeMonica If I'm not wrong, it alludes at the rule where you can trade toughness defence for other defences. For example,at PL 10, you can have 10 toughness and 10 dodge/parry, or you can have 15 toughness and 5 dodge/parry. \$\endgroup\$
    – Chepelink
    Commented Dec 7, 2019 at 0:21
  • \$\begingroup\$ Chepelink has the right of it. \$\endgroup\$ Commented Dec 7, 2019 at 16:56

Those changes are bad and you should not use them.

The problem is not relative power level. MM3 is not well-balanced to start with; this is well inside the noise.

The first problem is that this does not match the rest of the game system. MM3 does not use advantage/disadvantage mechanics anywhere else. That’s annoying but not too bad.

Worse, it’s going to make combat unfun. Taking down a high-toughness bruiser is already a swingy grind. You can generally expect to blanket-beat him eventually by stacking enough -1 penalties, and even a small amount of penetration supports that now. But adding an additional roll to that process and making it more likely that damage will be negated entirely draws that out. You likely won’t see that at the table much, because padded sumo is so unfun that they are likely to avoid those fights or play a different game.

  • \$\begingroup\$ I agree with you. But, I also think that impervious does very little to the PC unless they are fighting weaker foes. Weak enough to be, mainly, considered minions. And we know how easily minions are dealt. Would your answer change if this rule is meant to be for the pc rather than the NPC? \$\endgroup\$
    – Chepelink
    Commented Dec 4, 2019 at 14:28
  • \$\begingroup\$ @Chepelink my answer wouldn’t change. I think that’s slightly worse, since it would then come up more often. But really, high toughness is already fine. If you max it out, you’re going to be making most of those saves anyway. You’re right that impervious mostly means “ignore minions”, but you can already ignore them anyway. If you want a hard stop on damage, look at something like Insubstantial or Immunity instead. \$\endgroup\$
    – fectin
    Commented Dec 4, 2019 at 15:31
  • \$\begingroup\$ Fair enough, Although your answer do not answer the original question of "is this change OP", you gave me enough information to reconsider my position. I'll just wait a bit longer to see if not other answers pop-up. \$\endgroup\$
    – Chepelink
    Commented Dec 5, 2019 at 2:20
  • \$\begingroup\$ FWIW, Second Chance does work as a form of Advantage. \$\endgroup\$ Commented Dec 7, 2019 at 16:57

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