When originally forged, Soul Edge was just an ordinary sword, but after being bathed in blood and hatred countless times, the sword turned into a demonic weapon and gained a wicked soul, which the games called Inferno. Those who grasp its hilt are unable to escape its curse, as its spirit invades the mind like a parasite and drives its wielder insane. Its blade soaks in blood and in power, and it remains a polished red. Soul Edge is distinguished by its animate eye.
Consistently referred to as the Evil Sword throughout the series, Soul Edge has a reputation for devouring souls. The weapon is also known to be a shape-shifter – which form it takes depends on its current owner. Only those with great mental discipline can retain their will while wielding this weapon. In the games, a common trait of selecting Soul Edge as a combative weapon is that it depletes the health of the player whilst giving increased attack power or even draining an opponent’s health upon contact. Either way, it is not unusual for the player to lose the battle as a result of wielding the weapon – without the opponent actually landing the finishing blow – thereby living up to its in-game legend of “consuming” its wielder.
When Siegfried took the sword, he created the Evil Seed, a manifestation of the sword’s evil energy that caused disastrous negative effects.
Soul Edge’s curse is called malfestation, and is inflicted not only upon those who wield the sword itself, but those who come into contact with its shards.