Inscribe Sihedron (Su)
Replaces: Medium Armor
At 7th level, a sigilus learns to inscribe the Sihedron rune (the seven- pointed star that symbolizes all seven schools of Thassilonian magic) on a suit of light armor she wears. When she does so, her armor becomes physically empowered with defensive magic, granting her energy resistance 5 to two energy types of her choice selected from acid, cold, fire, electricity, or sonic, and increasing the armor’s armor bonus by 1. (Note that this increase is an armor bonus increase, and thus stacks with any enhancement bonus a suit of magic light armor may have.)
Inscribing the Sihedron rune in this way becomes part of the sigilus’s spell preparation ritual—she can inscribe a Sihedron rune in this way once per day as a result. Each day she inscribes the Sihedron rune, she can change the two types of energy resistance it grants as she wishes.
At 13th level, an inscribed Sihedron rune grants energy resistance 10 to one energy type and energy resistance 5 to two other energy types, and its armor bonus increases to +2.
A Sihedron rune can be inscribed only on light armor—it cannot be inscribed on medium or heavy armor, even if the magus later gains proficiency with medium or heavy armor.
This ability replaces medium armor and heavy armor.