During Link's adventures throughout Hyrule he will encounter several characters that will aid him in his quest by providing clues to a new item, helping other characters in need, or providing permission to access a new part of the world.
After defeating Morpheel in Lakebed Templeacquiring its Fused Shadow and removing the Shadow Crystal; if the hero returns to Lake Hylia he can meet Auru who will pass on his Memo written to Fyer who will add a new flight option for his cannon service and shoot the hero into Gerudo Desert.
After defeating Stallord in Arbiter's Grounds the hero can find the Mirror of Twilight however its found broken which cuts off access from the main world to the Twilight Realm. Its after this point where the hero must start seeking the fragments of the mirror scattered acrossed the world. If the hero returns to Zora's Domain he can acquire knowledge of a strange occurence that the local Reekfish are being taken and the last reported incident leads to the Snowpeak Province connected next to the zora home. Upon closer inspection the hero will meet with Ashei who will tell of her background and when she is informed of the occurrence earlier she will recount she saw a large creature with the local fish and she decides to quickly draw a Sketch which she hopes the zora can decipher and assist the hero further. This will eventually lead the hero to finding Prince Ralis praying to his fallen parents in Kakariko Graveyard and if the hero shows him the drawing he will note that Reekfish might be the best way to follow the trail of the creature as it has a very noticeable scent and offers a custom made bait he knows the fish like in the form of the Coral Earring.
After getting help from Rusl in re-entering the Sacred Grove the hero can return the Master Sword to its pedestal which acts as a key to unlocking the Temple of Time where one of next pieces of shattered mirror lay. After defeating Armogohma deep in the dungeon the hero reclaims the third missing piece of the mirror and proceeds to continue his search for final piece. Should the hero visit Castle Town and try approaching Hyrule Castle he will come acrossed a note written by Renado requesting his aid in Kakariko Village. When he arrives he finds an amnesiac Ilia and Renado suggests that Telma might be able to help find a cure for this phenomenon and writes a letter detailing the situation.
Returning to Telma's Bar the hero presents Renado's letter and she informs the hero of the local doctor who'd be the best fit to treat Ilia and writes him a invoice that details a debt for his service. When the hero presents the document the doctor does not have the medicine to help the hero and only a sample of it is laying on the floor broken from its container however according to the doctor a strange object was in Ilia's possession which got coated in the medicine's stinky odor.
After investigating the contents in wolf form the hero follows the trail of the medicine to the southern field area outside the town to discover nothing there however during the night time he will be ambushed by Stalehounds and after laying them to rest a strange statue can be salvaged from the beasts. This statue was given to Ilia by Impaz and if the hero shows it to Ilia this will prompt a resurgence of memory of said event and that the lady who helped her is in a Hidden Village.
With help from Ilia's recollection Gor Coron informs Chief Darbus to help clear the path that leads to the hidden village tucked away in Eldin Field. When the hero arrives on the scene he finds an abandoned old village home to some Bulblins which he dispatches with ease. After this the sole resident of the village comes outside to greet the hero she tells the hero of what happened to Ilia and that she was given a charm as thanks for rescuing her and she figures that'd help her remember all the good times she had together with Link since this was a precious item to her. Once the hero shows the charm to Ilia she is finally able to remember everything and as thanks she presents the hero with her most precious item the Horse Call as she loved taking care of Epona so much and that she'd love it if the hero would take the flute with him and Epona in his travels to always stay close to her in there hearts.