Armor of Scales

(Dragon Magic, page 15, DnD 3.5)

[Ceremony]

You imbue a target with the protection of a dragon's hide.

Prerequisite

Knowledge (religion) 4 ranks, Dragonblood subtype

Benefit

You gain access to ceremonies based on your ranks in Knowledge (religion). Each ceremony provides up to four participants with a minor natural armor bonus. The ceremony takes 30 minutes and requires you to mark defensive runes upon the arms and torso of each participant with ash from a burned wooden shield of particular quality (see below). The effect of each ceremony lasts for 24 hours. The natural armor bonus gained from this ceremony feat doesn't stack with a creature's existing natural armor bonus; use only the higher value.
Wyrmling Scales (4 ranks): Each participant gains a +1 natural armor bonus. This ceremony requires the ashes from a wooden shield of any size.
Adult Scales (12 ranks): Each participant gains a +2 natural armor bonus. This ceremony requires the ashes from a masterwork wooden shield of any size.
Wyrm Scales (18 ranks): Each participant gains a +3 natural armor bonus. This ceremony requires the ashes from a +1 (or higher) wooden shield of any size.