Warp to Vah Ruta in the Lanayru region, then fly east, cross the dam and keep going east to the yellow spot where you can hear Kass' accordion. While approaching, the monument's three stone pillars make some places appear. Kass says that his late master was talking about this in an unachieved song and that he's looking for the verses he was after to complete it.
"Reaching skyward from waters blue. Ruta's Champion a heart true.
The hero's power shall grow. Seek trials monuments show.
One, find what the light's path shows. Two, conquer the ancient foes.
Three, chase rings on the waterfall.
Champion, the trials call!"
Then Kass tells you about Zora's Domain where the King and his son told him about the Champion. Look closely at the places shown on the pillars to recognize eastern Zora's Domain, the islands all the way to the east of Lanayru and Upland Zorana in the northwestern part of Lanayru. Warp to Zora's Domain and ask King Zora to tell you about Mipha. He tells you about her diary where she wrote being in love with Link. Talk to Prince Sidon as well and ask him to tell you about the trial. He says that he sent Muzu and Tottika east of Ulria Grotto. Read Mipha's diary to learn more about your meetings, the Divine Beast and the fact that it can be manoeuvered.
Then, go to Mikau Lake to the east and go through the light ring. Quickly put on the Zora Armor, then go through all the rings within the time limit until a new shrine appears.
Mah Eliya Shrine - Secret Stairway
Go to the two metal crates, use Cryonis under the left one, then climb on it and notice another crate on the left. Go back on the elevated crate, use Magnesis on the other big crate, move it as high as you can, then let go, immediately use Stasis to freeze it as high as you can, then Cryonis to create an ice block under the frozen crate. Then, grab the third crate with Magnesis and place it above the second one. Climb the crates to reach the top of the room, then touch the monk's altar to receive a Ruta's Emblem.
Then warp to the Ke'nai Shakah Shrine in Ulria's Grotto, fly east, go up thanks to the updraft, then keep going northeast towards Knuckel Island. Muzu and Tottika are at the edge of the cliff. Talk to Muzu who says that a hundred years ago Mipha underwent a trial at this place and he gives you a riddle about a light path when the sun is rising at dawn. You can use the fire to make time pass quickly. At around 3 AM, the sun starts to rise, then at around 5 AM, it generates a line on the water. Fly towards the sun along this line, then you notice a blue ring in the sea. Go through it to make the trial appear.
Kee Dafunia Shrine - The Melting Point
Go ahead, shoot two Fire Arrows at one of the ice blocks to go through, then look at that big room. Step on one of the two switches which makes two ice blocks fall down towards the central platform. Then, shoot two other Fire Arrows (or shoot regular arrows through a torch) at the ice block the furthest from the centre. Climb on it, shoot two other arrows at the block closest to you on the platform, then jump on the blocks to end on the platform. (For a Frostblade, go back next to the last small block and melt the blocks under the footbridge to reach the chest.) Then, stand in front of the highest block with your back at the entrance. Use Stasis on the block, hit it 4-5 times to move it towards the monk. Go to it, shoot a Fire Arrow to reduce it a little, then move it in front of the wall. Generate an ice pillar under the block, shoot another Fire Arrow, then climb the pillar and the block to reach the monk's altar, who gives you another Ruta's Emblem.
Then warp to the Dagah Keek Shrine west of Zora's Domain, go up the waterfall to the west, then aim north for Upland Zorana where some Guardian Skywatchers and a Decayed Guardian are now. Start by destroying the Decayed Guardian with some arrows or some shield attacks, then attack the Guardian Skywatchers with some arrows as well. (You can check the Guardians Guide.) Once they're all defeated, another shrine emerges from the ground.
Sato Koda Shrine - Support and Guidance
Go forward and look at the falling orb, the three seesaws, as well as the container below to the right. Start by generating an ice pillar just to the right of the beginning's slope so it falls on the highest seesaw. Then, generate another pillar under the left part of this seesaw so it stays still and the orb goes down to the second seesaw. Then generate a third pillar under the right part of the third seesaw, but rather to the bottom so the orb touches it and falls in the middle of the four stone blocks. Now, wait for the orb to cross the first seesaw, then generate another pillar between the two pillars in the middle so the orb falls between the two lights, which causes it to bounce off and fall into the container to the right, which lifts the bars! Go next to this container, generate an ice pillar all the way to the bottom right, then generate another one partly under the chest's platform. Climb these two pillars, then generate another pillar more to the top right, climb it, jump to the chest and find a Giant Ancient Core. Finally examine the monk's altar to get a well-deserved Ruta's Emblem. Then the monk says you found the three Emblems and that you can go to the Divine Beast Ruta.
Warp to the beast and get close. A voice says that a new challenge awaits you which consists in facing your memories. You end up in front of Waterblight Ganon only equipped with Ceremonial Tridents, a Silver Bow and 10 arrows! and no meal! but on the other hand you have the four Champions' powers :-)
Waterblight Ganon - Illusory Realm
During the first phase don't use the arrows which will be vital during the second phase. Dodge his attacks, get close, use Stasis to freeze him, then hit him as much as you can with the trident. Repeat this 3-4 times to start the second phase. As during the first fight, the room's structure changes. Swim towards one of the platforms (not the one beneath the scourge) and use Cryonis to destroy the ice blocks he throws at you. Then use Revali's Gale to take off and shoot three arrows into his eye so he falls down. Quickly swim to his platform, freeze him with Stasis, then hit him as much as you can. You can also swim to the platform underneath him and use Urbosa's Fury to make him fall down. Repeat these steps twice, then Waterblight will fire a red beam at you. Use Daruk's Protection to repel his attack at him, which will make him fall down again, then swim, use Stasis again and hit him with, in theory, the last trident hits!
After your victory, you meet Kass who composed a new song about Mipha. A sequence shows Mipha getting visited by Princess Zelda and she asks her who the other Champions are. Then Mipha teaches her little brother Sidon how to swim up a waterfall. Afterwards, you receive Mipha's Grace + which now reloads faster.