Based off of Masamune, also known as Gorō Nyūdō Masamune (五郎入道正宗), is widely recognized as Japan's greatest swordsmith.

The Final Fantasy VII Masamune is an iconic symbol of the game, like the Buster Sword. It is the weapon used by Sephiroth, and he is said to be the only human who can use it even though Tifa wielded the sword at the Mako Reactor in Nibelheim, but without much success. Sephiroth uses this sword to murder Aeris at the Forgotten Capital by impaling her through the back.

The Masamune cannot be equipped in this game, but a similar version called the Murasame can be bought in the weapons shop in Wutai for Cloud Strife. The Final Fantasy VII design is seen with Sephiroth in every game and movie that he appears in, even appearing spontaneously when Sephiroth is reborn in Final Fantasy VII: Advent Children. This Masamune is easily recognizable due to its massive length, but thin width. It is an Odachi, a longer version of the Japanese Katana. A fake can be acquired as an item in the Speed Square of the Gold Saucer although it does nothing.

Sephiroth's Strength
What is his true power?

Even after appearing in so many titles, Sephiroth's true strength is still unknown. It's stated in the book, Reunion Files, that the Sephiroth seen in Final Fantasy VII: Advent Children has "ascended to a new level of existence" and is much stronger than before. But Sephiroth never used the full extent of his powers in the final fight against Cloud, and because of that his true potential is still unknown. Statements from Kitase and Nomura in the Director's Commentary of the Japanese DVD try to convey Sephiroth's power. Kitase said, "Sephiroth's existence and will is extremely powerful. There is nothing stronger, nothing above him." Producer Kitase even decided that they couldn’t make any other character stronger than Sephiroth in the world of Final Fantasy VII. A handful of characters besides Cloud, Elfé, Genesis Rhapsodos, and Zack Fair, are able to battle Sephiroth competently, but it is usually implied he doesn't exercise his full strength against most opponents.

Sephiroth is a highly skilled swordsman and is very strong and agile. In Crisis Core -Final Fantasy VII-, Sephiroth is able to defend himself with ease when facing both Genesis Rhapsodos and Angeal Hewley at once. Although Genesis gains a temporary advantage on Sephiroth one-on-one, Sephiroth quickly retaliates and forces Genesis on the defensive, and at this time he single-handedly cuts apart the cannon of the Sister Ray, slicing clean through it with one-handed strokes. Also, he can unleash bursts of energy from his sword and can teleport, and he retains the ability to unleash energy bursts in Last Order and Dissidia: Final Fantasy. As he has taken over Jenova's form, he is able to shapeshift her body parts into his visage and other forms. In Final Fantasy VII: Advent Children, Sephiroth is able to sprout his black wing at will, and in Dissidia: Final Fantasy, he sprouts it during his EX Mode. Sephiroth has his wing present at all times in the Kingdom Hearts series, and it is unknown if he can choose to manifest it or not.

Sephiroth also has a measure of psychic abilities, able to read minds, project illusions and levitate objects and people using his will alone. In Final Fantasy VII: Advent Children, Sephiroth retains his great strength and agility and demonstrates a limited control over the Lifestream that has been infected by those who died of Geostigma. Any other powers he has developed or retained since his death are not shown. Sephiroth's strength in the Kingdom Hearts series has caused him to be ranked among the harder bosses in the series. Sephiroth in both games is able to summon meteors, pillars of fire and orbs of dark energy.

The Supernova
Sephiroth's signature summon spell

Safer Sephiroth's ultimate ability, The Supernova. This summon spell lasts for over two minutes and is an impressive force. You will never forget the first time you witness the Supernova and watch in horror as your party loses their HP!

Summoned forth by Safer Sephiroth when both of his hands are raise, a meteor appears, destroying the Planets of the solar system, one by one. The meteor crashes into the sun, and because of this impact the sun starts to swell. It erupts into a Supernova, everything around is engulfed in the tremendous shock wave.