Prince Proteus is the tertiary protagonist in the Dreamworks animated feature film Sinbad: Legend of the Seven Seas. The long-time friend of Sinbad, almost sharing a mutual brotherhood relationship, and the ex-fiance of Marina, Proteus was destinied to become the next ruler of the kingdom of Syracuse. However, he was threatened by the goddess Eris, who devised a cunning scheme that it would result in the death of the future ruler and the fall of the marvelous city into glorious chaos. Eventually, Proteus was saved by Sinbad, who in return restored Syracuse into its previous state. While absent from most of the conflict, Proteus appears in the early and final events of Heroes vs. Villains, assisting Sinbad and the other hero forces in the fight against the villains.
Heroes Vs Villains War
Losing a Friend
While scouring the Seven Seas for hostile movements, Proteus joins forces with Sinbad on the flagship of Syracuse; the pirate brings a fabled ruby sunstone for Proteus and his men to examine. Sadly for them, the sea-witches Ursula and Morgana arrive with intentions to claim the sustone for Queen Grimhilde. No sooner the sea-witches get humiliated, Sinbad gets distracted from their initial defeat. However, Ursula seizes the opportunity to grab both the ruby sunstone and Sinbad in her tentacles before departing along with her sister, leaving behind the distraught Proteus to watch helplessly as his friend was taken by the sisters.
Reunion and Re-Match
During th in-between events of the battles, Proteus assembled the Syracusan royal guard to partake in Sinbad's release from Castle Grimhilde. Later, Proteus leads his flagship in the fight against Captain Hook in the seas of Germany, blasting the pirate to the Jolly Roger's cabin. There, he reunites with Sinbad and his companions; additionally, he joins the resistance movement to battle the remain forces of Grimhilde.
After Hook's defeat, the resistance focus on Ursula, the last lieutenant of Grimhilde on the ocean, intenting to strike her down once and for all. Though the sea-witch manages to flush most of the resistance's fighters, the remain heroes, including Proteus, unflur the sails of their ships, putting most of their compatriots at hold; additionally, Marina manages to kill Ursula by striking her through the abdomen using Prince Eric's ship's splintered bow. When the whale Monstro threatens the hero forces, Sinbad launched an ignited gunpowered barrel at the whale's mouth, blowing the monster apart.
The Road to Bald Mountain
After the battle against Grimhilde's forces, the resistance is tasked to stop the remaining villains led by Mok and Maleficent on Bald Mountain. While mobolizing their numbers into eastern Europe, the resistance finds the road blocked by Hades, who was tasked to hault their movement, and his monster, the deadly serpentine Hydra. As Sinbad, Proteus, and the Syracusan soldiers make their stand against the monster, the Hydra manage to overpower them with ease, growing more heads after the heroes sliced most of the original heads. Fortunately, a group of heroes led by 26, Littlefoot, Cera, Timon, and Pumbaa topple a barrage of heavy rocks atop the Hydra, crushing the monster. With their foe slain, the resistance mobilize their forces on Bald Mountain to meet with their adversaries.
The Final Battle
As soon as they defeat the vanguard of the villain forces on the outer rim of Bald Mountain, the heroes burst its way inside the power plant where Jasmine and Angel were held hostage, Confronting the remain villains, the resistance commence the final battle. During the fight, Proteus takes on Jafar's serpentine form along with Tack, and Sir Peter Dickison. Though Proteus manages to stun the beast, he is left opened to Jafar's attack. Rushing to his friend's aid, Sinbad push Proteus away, leaving him to be captured in Jafar's coils. Fortunately for him, Sir Peter unleashes his fiery breath, incinerating Jafar and draggin Sinbad out of hid coils. As the fight ensues, Sinbad, Proteus, and the other heroes contribute their effort in fighting the remain hordes of the villains, including the demonic minions of Chernabog and his Legion of Darkness. However, they are forced to retreat after the effects of the powerplant's portal's begin to overload. Most of the heroes escape just in time as the portal explode to smitherness.
Proteus and the remain survived heroes share empathy and compassion for the loss of innocent lives. After a short briefing, King Stefan and Merlin advise the heroes to return to their homelands, restore order, and stay vigilant for any other attack from their foes. Nonetheless, the leaders of the resistance host a huge celebration at King Stefan's castle for defeating their previous foes; Proteus looks on as Sinbad and Aladdin put aside their former grievances and form a mutual bond, joining the festivities all along. With peace stored, Sinbad, Prince Proteus, Marina, the Arabic pirates, and the Syracusan soldiers made arrangements to return to Syracuse, where they plan to restore order and maintain peace in the city.