Ragnarök is Chrona's Demon Sword partner. Ragnarök is the first inhuman weapon introduced in Soul Eater. It loves to degrade and pester Chrona (even during fights) by giving him noogies, pinching his nose, hitting him on the head, or taking his food. When Chrona finally tells Ragnarök to stop, Ragnarok seems surprised at his reaction. Ragnarök has taken to absorbing any soul, evil or not. By taken innocent souls, Ragnarök soul wavelength has grown out of control and vastly overpowers Chrona's own wavelength, which will lead to Ragnarök soul eating Chrona's soul in the end. Later on, Ragnarök can change its appearance to that of a dragon to give Chrona wings to fly vastly increasing Chrona's combat capablilties. It can also grow a mouth on its sword form that draws souls to it by using a high pitched scream. Then Ragnarök absorbs the souls, using the mouth like a vacuum. Also, while screaming in its sword form, Ragnarök acts like an electric saw due to the vibrations caused by its screaming. Ragnarök can control Chrona's black blood (due to consuming innocent souls) when it leave Chrona's body. It can use the blood spilled from Chrona's body to make spikes to attack anyone or can cause the blood to stop and act like a bandage for Chrona so it does not pass out from blood loss. When not in use, Ragnarök resides in Chrona's body, further tainting his blood and also allowing him to control Chrona's blood, Ragnarök commented that Maka's soul looked delicious. Whether Ragnarök can actually see souls has yet to been seen. He does worry about Chrona's health and will try to help Chrona by stopping his bleeding wounds. However, Ragnarök will always ask for thanks afterwards. After the fight with Maka Ragnarok had all his souls confiscated which resulted in him shrinking greatly in size (he now resembles a chibi form of himself) he is also slightly perverted since when Chrona finally stood up to him he acted like an understanding guy while at the same time pulling up Chrona's dress, also he lifted Maka's skirt and commented on her dull choice of panties. Even with less power he still wants to eat any soul he sees, he also tends to us Chrona as a human shield against non-deadly attacks like the Maka Chop.

Attacks: His attacks mostly concentrate using Chrona's blood and causing mass destruction.

Blood Spike: Changes the drops of Chrona's blood into spikes to attack from multiple angles.

Screech Resonance: Ragnarök's equivalent of Soul Resonance.

Jet Black Sword: a more powerful form of Ragnarök's sword form.

(Source: SoulEaterFan)