I know it's a stupid question but I'm wondering can anyone tell me how does doubling for critical threat range (from things like Improved Critical feat, Weapon Master etc...) work ?

I get that the doubled 20 is 19-20, doubled 19-20 is 17-20, but I don't get the rest like Rapiers and Scimitars 18-20 being 15-20 ?? and after that how it goes.

Thanks in forward and sorry for such a dumb question.

A weapon with 18-20 can crit on an 18, 19, or 20 (three numbers). Therefore doubling it means we need six possibilities to crit. So working down from 18 means we add on 17, 16, and 15. Which leaves us with 15-20.

Also note that it works differently in NWN1 and NWN2.

In NWN1, doubling of crit threats can stack, but it stacks ADDITIVELY. Not multiplicatively.

So if you have a Longsword (crit threat on a 19 or 20) and make it Keen (doubles threat range) and take the Improved Critical: Longsword feat (also doubles threat range) you get a TRIPLED threat range. Not quadrupled, as you'd expect. In this example, the longsword has a threat range of 15-20. (or 6 in 20, thrice as much as 2 in 20.) A Keen battleaxe (crit threat only on 20 if not Keen) with improved crit would get a range of of 18, 19 or 20. A rapier would get an amazing 12-20 threat range. (9 in 20, or a 45% chance to maybe score a crit.)

In NWN2, these multipliers do not stack at all. You can only double your threat range once. Even if you have both a Keen longsword and the improved critical feat, the threat range is only doubled. So a longsword can never get more than an 17-20 crit threat range.

Finally, the weapon master prestige class gets a flat +2 to the critical threat range at level 7. In both NWN1 and 2, this is added to the total AFTER all the multiplying happens. So the weaponmaster with the Keen Rapier and Improved Crit Rapier gets a total critical threat range of 10-20 in NWN1, 13-20 in NWN2. With a battleaxe, he'd get 16-20 in NWN1 and 17-20 in NWN2.

Ahh, now I undestrand more clearly, thanks guys.
+rep

yep criticals play a major factor in NWN1, but not so much in NWN2 unless you pick up weapon master levels to get their boost. In NWN2 they focused more on elemental/aura boosts over criticals. A +3 keen longsword in NWN1 with critical focus compared to a +3 longsword 1d6 fire 2d6 holy in NWN2, etc.

Is there, by any chance, a mod that changes the behavior to match NWN1?

Not that I know of.

NWN2 has the "correct" version of the rules anyway, which is to say it matches the pen&paper rules. Criticals could get a bit silly in NWN1. (Or a lot silly, with devastating critical.)

Actually, I would say that NWN1's rules actually match D&D 3rd edition, and there actually have been some criticism of the 3.5e decision to not have Keen and Improved Critical stack.

NWN2 only matches 3.5e, not 3e, in this respect.

As mentioned, NWN matches 3rd edition. Also, I don't really think it's silly to have Improved Critical and Keen actually stack for 15-20 on a Longsword (30% crits) or 18-20 on a Battleaxe (15% crits).

Stuff like a Scimitar critting on a 10-20 (55% crit) with Improved Critical/Keen/WM is a bit silly...but that's a problem with WMs and Scimitars/Rapiers/etc.

well I never found stacking silliy in NWN1 simply because its all about your build. You can focus on criticals or other things, so basically the rule change eliminates your choices and says "pick this method to build up your weapon damage, not how YOU want to do it."

A critical build in NWN1 is great sure, but your not going to do anything against things immune to criticals, just like building a sneak attack rogue is great, except for those things you can't sneak attack. It makes your build strong vs things that can be critical hit, and weak vs what cannot. Your not just given a critical build, you make choices to do it, which is the fun of roleplaying and doing different builds.

So in NWN2, they basically say "boost your weapons up with our elemental properties/holy/evil, etc and we thing that's better instead of what you think, so everyone of course loads up on the +5 iron weapons of death with acid/holy/evil etc damage or what ever. Which is really worst than eliminating criticals because stuff like undead, elementals, and all the other stuff that laugh at sneaks/criticals instead get mowed down by the super weapons.

To me personally, a dumb decision but hey we adapt. Warriors just pick up weapon master levels to get their criticals better if they want a critical build. Most probably ignore criticals and just make up some super weapons to mow down ANY foe fast instead of just the ones that can be critical hit.

Honestly, as long as the damage from a critical isn't so high it breaks the game completely, I don't see having a character who criticals more often than not being a major issue.

I am reminded of Monks in the original Final Fantasy and Alena in Dragon Quest 4 who would critical hit a lot, and the criticals themselves didn't feel completely broken. (FF1 Monks do feel broken at high levels, but that's due to getting high attack and double the usual number of hits, not so much the criticals, and that's counterbalanced by them being weak early in the game.) I also note that those are games in which arbitrary enemies can be criticaled, including slimes and jellies (especially Metal Slimes), and in which criticals ignore defense.

Hickory why no post on your five star account?

WM's also get a critical multiplier increase ;)

If I'm a fighter using a Morningstar, I'll do 1x damage 95% of the time and 2x damage 5% of the time for 105% damage overall. If I'm a WM using a scimitar I'll do 1x damage 45% of the time and 3x damage 55% of the time for 210% damage overall. The WM is literally doubling the fighter's damage...even without taking into account the extra AB the WM gets.

Hell, even a fighter with all the scimitar bonuses does 1x damage 60% of the time and 2x damage 40% of the time for 140% damage...which means the WM is still doing 50% more damage (again, without factoring in AB bonuses).

Not as much as you might think -- especially since WMs have massive AB bonuses as well. Or rather, if the WMs with full BAB and extra bonuses are struggling to hit an enemy, what's going to happen to the Fighter without those bonuses...or the rogue with 3/4 BAB and no bonuses either?

Why would it "heavily favor among bosses?" There's nothing inherent about bosses that makes them more likely to be crit immune.