Gorum's ArmorSource Inner Sea World Guide pg. 294 (Amazon), Gods and Magic pg. 17 (Amazon)
School transmutation; Level cleric/oracle 1, inquisitor 1, magus 1, shaman 1, warpriest 1
CastingCasting Time 1 standard action
Components V, S, M (1 iron spike)
Target 1 suit of metal armor or 1 metal shield
Duration 10 minutes/level
Saving Throw Fortitude negates (harmless); Spell Resistance yes (harmless)
DescriptionThe targeted suit of armor or shield sprouts thousands of tiny iron spikes like porcupine quills. These do not harm the armor’s wearer (though donning or removing armor under the effects of this spell takes twice as long), but they act as armor spikes or shield spikes (as appropriate). Any creature attacking the wearer with natural weapons takes 1 point of piercing damage for each attack that hits. At 5th level, the spikes gain a +1 enhancement bonus on attack and damage rolls; this bonus increases to +2 at 10th level. At 15th level, the spikes also gain the anarchic weapon quality.
Mythic Gorum's ArmorSource Mythic Origins pg. 12
The damage to attackers increases to 1d4 points of piercing damage and affects creatures that attack the wearer with a melee weapon, an unarmed strike, or a natural weapon. Melee weapons with reach do not endanger a creature in this way. If you’re wearing the armor and are taking bleed damage, the spikes lengthen and grow wicked barbs—this increases their damage against foes that strike you to 1d6 + 1/2 your caster level (maximum +5), and the spikes deal 1 point of bleed damage to any foe damaged by them. When your bleeding stops, the spikes immediately return to their normal size and any bleed effects caused by the armor end.