Mundus the Dark Emperor (lit. "World" in Latin) is the primary antagonist of the first Devil May Cry, and his defeat at the hands of Sparda two millennia ago sets the scene for the series.
Two millennia ago, he was born into the depths of the Demon World, and quickly rose to power. He planned to lead an assault on the Human World. However, one of his chief generals, Sparda, "awoke to justice". Sparda then single-handedly defeated both Mundus and his armies and sealed the main gate into the Demon World.
At the end of Devil May Cry 3, as Sparda's son Vergil wanders the Demon World, he comes upon Mundus and challenges him. However, he is defeated, and transformed into Nelo Angelo.
In Devil May Cry, Mundus attempts to escape into the Human World by opening a gate on Mallet Island. At the same time, he uses Trish to manipulate Sparda's other son, Dante, into coming to the island so that he can be killed. Although Dante does come to the island, he is able to defeat Mundus and his minions. Mundus then falls back into the Demon World after Dante blasts him with super lightning charged Ebony and Ivory. To use the super charged Ebony and Ivory, you must have at least three Devil Trigger Gauge symbols full.
In Devil May Cry 3, and during some parts of Devil May Cry, Mundus appears as three glowing orbs arcing with energy. It is uncertain if this is his true form, or merely an avatar. Mundus also appears as a marble statue of a three-eyed, angelic youth with long hair. This form then takes on an appearance of a older, bearded man with a big hole in his chest (Probably a scar from his battle against Sparda). During his final battle with Dante, the marble breaks away, revealing a grotesque, writhing being made of lava, with three eyeballs and a mouth attached by stalks to its head.
Mundus appears to have been worshiped by the residents of Mallet Island, as there are many statues to his angelic likeness situated about the castle, and Dante comes across many clues of strange rituals during the game. However, it is also possible that these were instead constructed by the demons Mundus fills the island with.
The mundus Cereris was a pit in Roman mythology. It contained an entrance to Hades, the underworld, which was ruled by Pluto, the Roman god of the underworld; Mundus is identified as Pluto twice within Devil May Cry. The stone covering the pit, known as the lapis manalis, would be removed three times a year, and when it was removed it was believed that the spirits of the blessed dead would commune with the living.
Mundus' three eyes are likely a reference to Satan, who is portrayed with three faces in Dante Alighieri's The Divine Comedy. Satan is also considered the "prince of this world" and the "prince of darkness". Mundus shares both of these titles.
(( Above )) Sparda's Human Form
Sparda is the demon responsible for defeating Mundus two thousand years ago, and is the father of Dante and Vergil.
In his human form, Sparda was very similar to his sons. His hair was swept back, and he is always portrayed as wearing a monocle and purple jacket. In his true form, Sparda was a human sized demon, with cloven hooves, a semi-reptilian hide, a pair of sweeping horns, two pairs of insectoid wings and one pair of chiropteran/bat wings. His entire body appears to be made of grey armor with accents and overtones of tyrian purple, and features ornamental decorations, such as gold trim along his "crown," a vertical red gem in his forehead, as well as gold knee and elbow guards. It is unknown if these are part of an external armor or whether they are natural features of his anatomy.
Sparda was once one of Mundus' Devil Knights, and apparently took part in the invasion of the human world. At some point however, he suffered a change of heart and switched sides, fighting to protect the humans. He defeated Mundus' demon armies, before moving onto the Prince Of Darkness himself. Sparda defeated Mundus, and sent him and his armies back to the demon realm. In order to close the gateway, Sparda used his own blood, along with the blood of a human priestess, in conjunction with his sword and a mystical amulet. Pouring his demonic energy into the sword allowed him to close the door between realms, however this also robbed him of the lion's share of his abilities. Sparda could still access his powers when he used the amulet but only for a brief time. Sparda's activities over the next two thousand years are shrouded in legend, however it is understood that for a time, directly after defeating Mundus, he ruled over the humans before eventually vanishing. Devil May Cry 3 raises an interesting plot element, as it would seem that Sparda sacrificed his powers only to seal off the full functions of the Temen-ni-gru, as according to the Order of the Sword and by Dante's admission, Sparda sealed the true hell gate by using Yamato. He showed up again in the twentieth century where he met and fell in love with a human woman named Eva. He fathered the twins and for a brief time lived with his family, before he again disappeared. Many believe he died, although in DMC2 Dante hints he may have passed into another realm. Though Sparda likely did die because in DMC1 during the intro a narrator voice told a story of Sparda (As the words are rising up you see Sparda in the background in his devil form displaying his skill with his sword and in a fiery background) and said that he "continued to preserve harmony until his death, and how he became a legend, the Legendary Dark Knight Sparda.
Arkham uses the Sons of Sparda to open the gate to the Netherworld, in order to obtain the Force Edge and thus the powers of Sparda. While he is able to use it to temporarily take on Sparda's form, he is unable to truly resonate with it and soon mutates into a hideous demonic blob.
Intro "Two milleniums ago there was a war. Between the human world and the other... the Underworld. But somebody from the Underworld woke up to justice, and stood up against this legion, alone. His name was Sparda. Later he quietly reigned the human world, and continued to preserve harmony, until his death. He became a legend, The Legendary Dark Knight, Sparda.
Sparda is referenced frequently throughout the game. At the start of the battle with Mundus, Dante finally awakens the true powers of Sparda's sword, and assumes Sparda's form as a new Devil Trigger. In this form, Dante can fly, shoot fireballs from his fists, and summon a spectral dragon. While fighting on the ground during the second part of the boss battle, Dante can also charge the fireballs, and the range of his sword is greatly extended.
It is revealed that Sparda once had two apprentices, twin brothers Baul and Modeus.
The Order of the Sword is a group of demon hunters that worship Sparda. Nero, the main protagonist of Devil May Cry 4 is also blood linked to Sparda, and referenced multiple times in Sparda's likeness in power and appearance.
Dante mentions Sparda once crossed into the demon world and returned. It is also revealed Sparda once fought against Argosax and Bolverk.
The exact extent of Sparda's powers remains unknown; but it is shown that his powers surpassed even the "Prince Of Darkness" himself. However, it should be noted that the Gryphon boss in the first Devil May Cry admonished, after being defeated for the final time, that "Yours [Dante's] are definitely the powers of Sparda... No, even more so." In Devil May Cry 3: Dante's Awakening, Arkham connected the absorption of Sparda's power to reaching the pinnacle of demonic power and essentially becoming a God. It has been claimed that Dante's powers have surpassed Sparda's power by a hundred times.
Sparda used the Yamato, and also sealed his power into the Force Edge, his own trademark weapon. It is said that he also used the Luce & Ombra.
(( Above )) Sparda's True Demon Form