Bâo-Lèi Sword

The Bâo-Lèi Sword (宝レイ剣, lit. Treasure Thunder Sword) is a silver sword and the most treasured heirloom of the Tao Family.

About
The Bâo-Lèi Sword is an ornamented sword with a collapsible blade and a purple tassel at the end of the hilt.

It posses spirit refining abilities and was able to evolve Bason from a Human Ghost, to a Seirei Class spirit by merely being used as a medium for the Over Soul.

It was first seen used by Tao Yúan as the medium for his Dà Dào Lóng Over Soul but was later passed on to his son Tao Ren. After Asakura Hao had the Spirit of Fire incinerate Ren's Kwan Dao to dust during the Second Round of the Shaman Fights, Ren would go on to use the Bâo-Lèi Sword as the main medium for his Over Soul.

Anime/Manga Difference
In some translations, it is known as the Houraiken, which is the on'yomi rendering of the name's pinyin, Bâolèijiàn.

Trivia

 * One portion of the swords name for some reason, is rendered in katakana instead of in hanzi/kanji (レイ instead of 雷).