Jewel of Four Souls

The Shikon no Tama (&#22235;&#39746;&#12398;&#29577;; lit. Jewel of Four Souls) or "Shikon jewel", is a fictional, magical jewel in the anime Inuyasha.

The Four Souls
The four souls described are from the philosophy of Naobi (&#30452;&#38666;): Courage (&#33618;&#39746;, aramitama), Friendship (&#21644;&#39746; nigimitama), Wisdom (&#22855;&#39746;, kushimitama) and Love (&#24184;&#39746;, sakimitama). When all united in one person, such as Midoriko, they unite to form a powerful balance within the soul that can be used for good or evil.

Background of the jewel
The jewel was created by the battle of the great miko (priestess) Midoriko and powerful youkai (demons). Her power came from using the four souls for good. The battle continued for 7 days until one youkai managed to attack Midoriko by creating a counterbalance of the four souls for evil through a human who secretly loved her, similar to how Onigumo loved Kikyo creating Naraku.

Midoriko, realizing that she would be unable to fight off the youkai group using the four soul power and facing defeat, forced out her own spirit and bound the youkai into a jewel prison with the last of her power, killing both of them and creating the Shikon no Tama. The balance of energies created a jewel in which they are always battling with neither winning over the other and which has great powers that can be used for good or for evil.

The jewel was controlled by various humans and youkai for several centuries until it ended up being rediscovered by Sango's grandfather in the Mistress Centipede. Before the series begins, Sango's father entrusts Kikyo with the guardianship of the jewel due to her purifying powers, but it leads to her untimely demise and Inuyasha (who loved her) being sealed to a tree for 50 years, when Naraku deceives them into hating each other by making them think they had attacked each other so that the jewel would be filled with their hatred.

The jewel was burned with Kikyo and only returned 50 years later through a reincarnation of Kikyo, Kagome coming back from the future because of the Jewel's power and the interference of the youkai, Mistress Centipede. Kagome eventually unsealed Inuyasha, however the jewel was lost to a demon-crow. In attempting to retrieve it by shooting the crow with an arrow, Kagome accidentally shatters the jewel, which is now in thousands of shards (Shikon no Kakera). Inuyasha-tachi (Inuyasha, Miroku, Kagome, Shippo and Sango) are attempting to collect the shards and stop Naraku.

Form of the Shikon Jewel
Physically, it is a sphere that appears to be made of some sort of crystalline material prior to the accident that shattered it. When purified, the jewel is a soft pink color, however the more tainted the soul and wishes of the person holding it, the more the color turns to a lurid black-violet. It is somewhere between a marble and a ping-pong ball in size when complete, but the shards of the Shikon-no-Tama are irregular in size and shape.