Vah Ruta is a mechanical construct in The Legend of Zelda: Breath of the Wild. It is one of the four Divine Beasts. Vah Ruta is made from Ancient Sheikah technology; it takes the form of a giant elephant in the East Reservoir Lake in Lanayru Great Spring. Ganon sent Waterblight Ganon to corrupt it, transforming it into one of the main dungeons. Link must defeat this boss to free Vah Ruta.
Ten thousand years before the events of Breath of the Wild the Sheikah created Vah Ruta which was named Ruta after the Zora Sage Princess Ruto and entrusted to the Zora people. Piloted by an unnamed Zora Champion, Vah Ruta and the other Divine Beasts supported the Goddess-Blood Princess of Hyrule and Hero Chosen by the Master Sword in defeating Ganon who was sealed by the Princess. For a time the Divine Beasts were venerated though eventually people began to fear the misuse of Sheikah technology including the Divine Beasts. The Sheikah that remained loyal to Hyrule chose to bury their technology including Vah Ruta so it could be used to combat Ganon in the future when he inevitably returned to plague Hyrule once more. Over time the technology was lost and faded into legend.
One hundred years before the events of Breath of the Wild, Rhoam Bosphoramus Hyrule, his daughter, her personal Royal Knight Link, along with four new Champions sought to seal Ganon through the use of the Divine Beasts and Guardians as their predecessors had done in the distant past. Vah Ruta was discovered and excavated in the Lanayru Great Spring region where Zora's Domain is located. Young Princess Mipha was drawn to Vah Ruta which she found to be cute and spoke of it as if it were a friend. Eventually Zelda requested Mipha piloted Vah Ruta which she agreed to as it would allow her to aid her beloved childhood friend Link whom Mipha was in love with and wished to marry once Ganon was defeated. Mipha mastered piloting Vah Ruta almost effortlessly and her father King Dorephan took her connection to Vah Ruta as a sign she was fated to defend Hyrule alongside the hero as Princess Ruto had done before her. Dorephan supported Mipha's decision to pilot Vah Ruta as Ganon was an enemy to all of Hyrule including the Zora. However Mipha's teacher Muzu and combat instructor "Demon" Sergeant Seggin opposed it with Muzu even walking out during the meeting while Seggin could bare to look at her though they both simply feared for her safety as the dreaded King of Evil was no ordinary foe. However Mipha was determined to aid Link and protect her people and Hyrule from Ganon who made his return on Zelda's seventeenth birthday.
Unfortunately Ganon was no fool and having learned from his past defeat took control of Vah Ruta and the other Divine Beasts, turning them against the people of Hyrule and robbing them of the tools which had previously saved Hyrule from Ganon's evil. Mipha met her demise by a creation of Ganon known as Waterblight Ganon, who then assumed control of Vah Ruta for the next one hundred years though it became dormant as a result of Zelda sealing herself and Ganon in Hyrule Castle.
Unfortunately Vah Ruta awoke a century later endangering Zora's Domain and everyone who lives outside of it by flooding the East Reservoir Lake. If the Rutala Dam broke, it would completely destroy Zora's Domain and cause a chain reaction that would send a significant amount of water throughout Hyrule, if not flood it completely as the reservoir had been created 10,000 years ago to prevent flooding that occurred in the region every decade due to increased rainfall.
The Zora became desperate for the aid of a Hylian; the weapons used to subdue Vah Ruta, Shock Arrows, are too dangerous for a Zora to touch, let alone use, given their vulnerability to electricity. However, most of the Zora Council of Elders blame the Hylians for Mipha's death and prefer not to ask for their help, most notably Muzu and Seggin.
After Link talks to King Dorephan and Prince Sidon, and puts Muzu's doubts about Link to rest, Sidon and Link meet up at East Reservoir Lake, assuming Link has a sufficient amount of Shock Arrows. If Link does not, he must go up to Ploymus Mountain, steal some Shock Arrows from the resident Lynel, and then travel to East Reservoir Lake and meet up with Sidon.
From there on, as the duo approach Vah Ruta, Link must get rid of the cubes of ice by either using any type of Arrows or he can use the Cryonis Rune as a means to counter the ice cubes. When Sidon climbs up a waterfall on Vah Ruta, Link must be prepared to aim a Shock Arrow at one of the switches on the Divine Beast's sides. Every time this is done successfully, Vah Ruta starts becoming more aggressive with its attacks: adding more ice cubes and eventually ice mines that pursue Link and Sidon. When all four switches have been hit, Link can then proceed inside Vah Ruta, find the terminals of Vah Ruta, and encounter the Scourge of Vah Ruta, Waterblight Ganon.
Once Link frees Vah Ruta from Waterblight Ganon's control, Mipha resumes control of it, gives Link Mipha's Grace, a powerful healing spell that brings Link back from the brink of death, and takes the Divine Beast to the peak of a mountain, where it directs a targeting laser towards Hyrule Castle. If all four Divine Beasts are freed, they will fire powerful beams of energy that reduce Calamity Ganon to half-health.
In the true ending, Zelda mentions that Vah Ruta had mysteriously shut down, and thus she and Link need to head over to Lake Hylia to investigate.
The name for Vah Ruta, like all four of the Divine Beasts, is based on a sage from a past installment the Legend of Zelda series. The Ruta name is a reference of the name of the sage of water, Ruto, from The Legend of Zelda: Ocarina of Time.
Vah Ruta appears to specifically be based on the African elephant, since the size of its mechanized "ears" are large in relation to its head. Vah Ruta also makes the iconic trumpeting sound of an elephant, which is common among the African ones while Asian elephants often make chirping noises rather than the trumpets alone. In addition, Vah Ruta noticeably has large tusks, which is a feature unique to African elephants, only some Asian elephants have tusks, and they are quite short.