Fire-opal

_“ The fire-opal is the light from the eye of the Great Auroch. That's why the demons are drawn to it.
—Renn about the fire-opal, Soul Eater, chapter 26

The fire-opal is a powerful stone used by the Soul-Eaters to attract and control demons. As long as it does not touch the ground, whoever wields the fire-opal has absolute control over the demons. The original stone was shattered into three pieces by Torak's father, in an attempt to destroy the Soul-Eaters' power. But the pieces survived, just as powerful. They were wielded by the remaining Soul-Daters in the course of the series.

The fire-opal in the Russian cover of Soul Eater

Appearance

The fire-opal, and it shards, are described as very beautiful and fiery red, with a glow likened to fire. It was however cold to the touch, such that Wolf described it as the "Bright Beast That Bites Cold", contrast to the "Bright Beast That Bites Hot" (fire). It was in fact so beautiful that Torak's Fa couldn't bring himself to destroy one piece, so he instead concealed it inside the hilt of his knife, which he passed on to his son at his death.

The fire-opal in Fa's knife in the Russian cover of Outcast

Method of destruction

To destroy the power of a piece of the fire-opal, it must be buried in the earth together with a living soul, which must die with it.

Significance in story

Wolf Brother

The first fire-opal shard was used by Tenris to capture an elemental demon and trap it inside a bear, thereby creating the demon bear which killed Torak's Fa.

Spirit Walker

Tenris the Seal Mage used a fire-opal shard shard to summon demons to make two tokoroths to do his bidding. When Tenris drowned in the sea, his shard went undiscovered since he'd hidden it in a shrine.

Soul Eater

Four Soul-Eaters, Nef, Thiazzi, Eostra and Seshru, used the second fire-opal shard in a demon summoning rite that involved the murder of hunters. This shard was ultimately destroyed when Nef sacrificed herself by pluging into a crevasse with the opal in her hands.

Outcast

Torak discovers the third fire-opal shard hidden inside his Fa's knife hilt. This piece is smashed when Seshru the Viper Mage demanded that Torak give it to her. And when Seshru tries to gather the fragments she is shot by Bale in the heart and dies, this piece thus dies with her.

Oath Breaker

Thiazzi finds Tenris' shard of the fire-opal at an altar at Seal Island. Eostra's eagle owl snatches the shard from him during his final showdown with Torak and flew away to deliver it to Eostra.

Ghost Hunter

Eostra used the last remaining fire-opal shard to summon the spirits of the deceased soul eaters in order to bring them back to do her bidding. Torak snatched the shard from her and destroyed it, thereby destroying the last fragment of the fire-opal and putting an end to the Soul-Eaters' power.