Incorporeal beings ignoring normal armor and shields. But the ring of force shield provides a force effect. Does that work, as force-effects work on incorporeals?
1 Answer
Yes, it does
Ring of Force shield states:
An iron band, this simple ring generates a shield-sized (and shield-shaped) wall of force that stays with the ring and can be wielded by the wearer as if it were a heavy shield (+2 AC).
The Wall of Force Spell has the [force] keyword
Incorporeal Creatures say:
An incorporeal creature’s attacks pass through (ignore) natural armor, armor, and shields, although deflection bonuses and force effects (such as mage armor) work normally against it.
Emphasis mine.
Since the Ring duplicates a spell with the [force] keyword, it is a force effect and thus would work normally against incorporeal creatures.
References:
http://www.d20pfsrd.com/magic-items/rings/ring-of-force-shield
http://www.d20pfsrd.com/magic/all-spells/w/wall-of-force
http://www.d20pfsrd.com/bestiary/rules-for-monsters/universal-monster-rules#TOC-Incorporeal-Ex-