The Heart Gem
The Heart Gem is a deep rich purple color.
The Heart Gem is one of the Four Universal Jewels (the others being the Soul Gem, the Karma Gem, and the Mind Gem). Combined, these four gems form The Unity Stone, which (legend has it) bestows god-like powers to the possessor. The Chosen One is prophesied to combine the gems and guide the unification of all the planes of existence into true, lasting Oneness.
The Gem bestows upon its wielder power over the emotions of others.
The four Gems were scattered a thousand years ago, after a mad cleric managed to combine them briefly and threatened all of existence.
This Gem is in the possession of Sophia Beaulieux, aka the Mistress of Gaea, who used it to manipulate the emotions of key players in the Sri Lankan government and military to effect her coup.