Guardian Gem

Aspect: Earth
Rating: ••••  
Manse: Pinnacle of Mercy, An-Teng
Bearer: The Golden Lord of An-Teng. 
Source: Based on original by Ikselam on the Unofficial Exalted Wiki.

This hearthstone resembles a very large rough diamond. When attuned, it causes a thin film of flexible adamant to form on the bearer's skin. If the bearer wishes, this film can instantly harden into impenetrability, channeling the full force of a blow into the Guardian Gem. Mechanically, the character may choose to reflexively activate this power in response to an attack which hits them, after regular soak but before any damage or other effects are applied. The attack does no damage, and produces no other effects; all of its force and power is redirected to the hearthstone (including any perfect damage/additional damage/additional effects declared after the stone is activated).

Using the Guardian Gem's special power causes it to immediately shatter, but it will reform at its Manse as normal. Use of the power also causes the adamant shell surrounding the character's body to disintegrate into a myriad of brittle shards, which quickly flake off her skin and disintegrate into sand. Particularly powerful attacks may cause the adamant shell to burst forcefully off her body, flying through the air to shatter harmlessly (but impressively) against the ground, her attacker, and anything else which may be nearby.