Murakumogiri is a naginata that was used by the Yonko Edward Newgate until his death.
Whitebeard acquired Murakumogiri sometime after his childhood.
He was first seen with it during the Great Age of Pirates, when he took control over Fish-Man Island.
Whitebeard died on Marineford two years ago with Murakumogiri in his hand, and it was placed on his grave near Sphinx, with Whitebeard’s Jolly Roger and coat hanging from it, and remained there since.
With Whitebeard’s immense power and skill, Murakumogiri was strong enough to clash with Shanks’s saber, which caused the clouds (and even the heavens) to split.
Murakumogiri could be used in conjunction with his Devil Fruit and Busoshoku Haki to increase the already great damage it could inflict, as well as to neutralize any potential Devil Fruit defense his opponents may possess.
Murakumogiri is extremely durable, having stopped Akainu’s magma attack without melting or receiving any visible damage, though this may have resulted from Whitebeard coating it with Busoshoku Haki.
Oda has just revealed in SBS Volume 93 that Murakumogiri is one of the 12 Saijo O Wazamono, the 12 Supreme Grade Swords just like Yoru(the blade currently owned by Dracule Mihawk) and Shodai Kitetsu.
The 12 Supreme Grade Swords are the highest quality swords in the world. Murakumogiri is the only known Meito that is not a sword.