Improved Grizzled Hide

From AoCWiki

Adds 1%, 2%, and 3% to all invulnerability ratings.

With 3 points invested it negates 3% of the 10% invulnerability defence ratings that Aspect: Untamed Regeneration causes.

So if you get Aspect: Untamed Regeneration it's highly advisable to put 3 points in this feat also

At lvl80 with 3 Feat Points: +3% vs ALL Invul. +31.9 Defense Rating