Dumb Question about miss chances

[LOTRfan]

As the title says, I have a question about miss chances and stacking. Natural Invisibility grants a creature a 50% miss chance. The incorporeal subtype does the same (provided the weapon is magic).

When a creature has both, do the effects stack? Is a creature with both abilities pretty much invulnerable? Do you need to make two separate rolls for the attack to see if it can get past both natural defenses? Does it not stack at all, and only give a 50% bonus?

[Lycar]

Given that invisibility miss chance designates actually connecting with your target and that incorporeal miss chance designates your magic weapon interacting with your target in a way significant enough to cause actual damage, I would say yes, these miss chances stack.

Which means that, on average, only 25% of 'hits' will end up inflicting actual damage, since you do indeed roll for both miss chances.

About 37,5% of 'hits' if the attacker has the Blind Fighting feat.

This still doesn't make said creature invulnerable though, it just means it has, effectively, a very good AC. :smallwink:

Lycar

[JBento]

Miss chances are always separate rolls. Some of them stack, some of them don't (Blur doesn0t stack with inivisibility).

If you want, besides incorporeality and invisibility, you can stack a lovely (Improved) Blink spell, and they all stack, redcuing hits to an average of of 12.5%

[Cog]

Multiple concealment conditions don’t stack. If a creature receives miss chances from multiple sources, such as from being incorporeal and having concealment, only the highest miss chance applies.
So, by default, the chances don't stack. However...

It usually isn’t worth differentiating between more degrees of concealment. However, the DM can rule that certain situations provide more or less than typical concealment, and modify the miss chance accordingly.
If the DM decides that a different source of 50% miss chance is a 'certain situation', then so it is.

[Curmudgeon]

If the DM decides that a different source of 50% miss chance is a 'certain situation', then so it is.
My take as a DM: I use that second RC rule to make the miss chance exactly what it would be without the first rule. :smallbiggrin: (That is, I ignore Rules Compendium's conflating of all miss chances with concealment, and go back to the rules in the Player's Handbook. So miss chances of different types stack, just as originally specified.)