Before you head off on your search for the Royal Bow, it's worth having a read of Zelda's research notes. In this guide we're going to point towards two interesting in-game pieces of text, and then below that we'll transcribe them for anyone who finished the game without finding these texts. They're worth reading even if you don't want to make a trip into the castle.
First up, you'll want to check out our Hyrule Castle memory guide, because the books and bow are on either side of the bridge you need to visit to find that memory. In Zelda's study, inside the spire, you'll find a notebook containing her research notes.
Read these over to find out more about the lore of this world, or scroll down further in this guide for a transcription.
Cross the bridge and head through the doorway. It's time to go get the Royal Bow.
You'll need to jump through this hole to enter Zelda's room, where the bow and diary are kept. They're guarded by a lone Lizalfos, but getting rid of him shouldn't be too much of a problem. Once you kill it, enjoy the room's reworked version of Zelda's lullaby as you explore.
Check above the fireplace for the Royal Guard's Bow, which packs a real wallop.
Hold onto this bow for your final fight with Calamity Ganon – it shoots three arrows at once (without using extra ammo) and has a very high damage rating, but its low durability means that it'll break pretty fast. Don't waste it!
In the western corner of the room is Zelda's diary. If you visit, give it a read - it gives some great insights into the state of mind of both Zelda and Link 100 years prior.
If you want to know what it says, but you've finished the game already and don't want to revisit Hyrule Castle, keep reading.
Zelda's research journal
Page 1: "Today I met with Impa of the Sheikah tribe and began my research into the ancient technology in earnest. Impa introduced me to Purah and Robbie, other respected members of her tribe. Tomorrow I embark on an excavation with them. We hope to find ancient tech with which to operate the Guidance Stones."
Page 2: "Today we uncovered some ancient technology that we believe may have the power to control the Guidance Stone. It is a rectangular object, small enough to be held with two hands. Sheikah text is featured prominently in it. It is made of an unknown material, but we believe it is the same as the shrines scattered across each region. Impa proposed that I hold on to it for now. I hope that it leads to some new developments in our research."
Page 3: "The stone relic we discovered has been named. We are calling it the Sheikah Slate. We have not found any mention of a name for this object in the records we have unearthed so far...Nevertheless, Purah insisted we call it the Sheikah Slate, as the relic is a slate made by the Sheikah tribe. Feels a little on the nose to me, but it was not a fight I thought I could win."
Page 4: "We did it. We were finally able to restore some functionality to the Sheikah Slate. We have discovered that this stone slate is capable of producing...images. Perfect likenesses of the things you point it at. Unlike normal pictures drawn by hand, this requires no artist to capture anything in important detail. I deeply admire the accomplishments of Sheikah technology. Still...I know there is more to learn. There must be. We believe the Sheikah Slate may have a function that will allow it to control the Guidance Stone. We must continue our research, and quickly."
Page 5: "We have started training the Champions who will pilot the Divine Beasts. It may sound rude that I found this unexpected, but Mipha mastered the controls with surprising ease. Daruk struggled at first but eventually got the hang of it. Urbosa and Revali both managed just fine as well. I can finally see the light of hope in our fight against the rising Calamity."
Page 6: "Robbie has restored mobility to many of the Guardians we've excavated ... But we still have yet to find all of the Guardians. Records mention a greater number of them - and even other types. They are said to be stored in five giant columns that rest beneath Hyrule Castle. The thing is...No matter how I search beneath the castle, I can't seem to locate these columns. They must be buried deep. Were they perhaps designed to sense the approach of Calamity Ganon and to only activate upon his return?"
Page 7: "Countless ancient structures are being discovered across Hyrule...but all attempts to enter them have failed. Records indicate that these are facilities designed to train the hero who is fated to combat the Calamity. But the crucial activation mechanism remains a mystery. Is the Sheikah Slate the key to activating them? That is Purah's theory, and I concur. And yet, my experiments so far have been fruitless. Still, we must exhaustively investigate all means of opposing the Calamity. We must not give up, no matter what!"
Page 8: "I spoke with Purah about the Shrine of Resurrection we discovered earlier. As we speculated, this particular shrine is, in fact, a medical facility with the power to heal. It also has a long-term stasis function that can be activated and maintained until healing is complete. In the war against the Calamity, 10,000 years ago ... were the injuries so great as to necessitate such a facility? If so, I will remain uneasy until we have made all adjustments necessary to restore it to full working order. I can only pray that even if Calamity Ganon returns, our battle will not require the Shrine of Resurrection's power ...
Page 1: "After meeting with the Champions, I left to research the ancient technology, but nothing of note came of my research. The return of Ganon looms - a dark force taunting us from afar. I must learn all I can about the relics so we can stop him. If the fortune-teller's prophecy is to be believed, there isn't much time left...Ah, but turning over these thoughts in my head puts me ill at ease. I suppose I should turn in for the night. P.S. Tomorrow my father is assigning HIM as my appointed knight ..."
Page 2: "I set out for Goron City today to make some adjustments to Divine Beast Vah Rudania. I still recall feeling his eyes on me as I walked ahead. The feeling stayed with me so long, I grew anxious and weary. It is the same feeling I've felt before in his company...And still, not a word passes his lips. I never know what he's thinking! It makes my imagination run wild, guessing at what he is thinking but will not say. What does the boy chosen by the sword that seals the darkness think of me? Will I ever truly know? Then, I suppose it's simple. A daughter of Hyrule's royal family yet unable to use sealing magic ... He must despise me.
Page 3: "I said something awful to him today ... My research was going nowhere. I was feeling depressed, and I had told him repeatedly not to accompany me. But he did anyway, as he always does, and so I yelled at him without restraint. He seemed confused by my anger. I feel terribly guilty ... and that guilt only makes me more agitated than I was before."
Page 4: "I am unsure how to put today's events into words. Words so often evade me lately, and now more than ever. He saved me. Without a thought for his own life, he protected me from the ruthless blades of the Yiga clan. Though I've been cold to him all this time ... taking my selfish and childish anger out on him at every turn ... Still, he was there for me. I won't ever forget that. Tomorrow, I shall apologize for all that has transpired between us. And then ... I will try talking to him. To Link. It's worth a shot."
Page 5: "Bit by bit, I've gotten Link to open up to me. It turns out he's quite a glutton. He can't resist a delicious meal! When I finally got around to asking him why he's so quiet all the time, I could tell it was difficult for him to say. But he did. With so much at stake, and so many eyes upon him, he feels it necessary to stay strong and silently bear any burden. A feeling I know all too well ... For him, it has caused him to stop outwardly expressing his thoughts and feelings. I always believed him to be simply a gifted person who has never faced a day of hardship. How wrong I was ... Everyone has struggles that go unseen by the world ... I was so absorbed with my own problems, I failed to see his. I wish to talk to him more and see what lies beneath those calm waters, to hear him speak freely and openly ... And perhaps I, too, will be able to bare my soul to him and share the demons that have plagued me all these years."
Page 6: "Father scolded me again today. He told me I am to have nothing more to do with researching ancient technology. He insisted that I focus instead on training that will help me awaken my sealing magic. I was so frustrated and ashamed I could not even speak. I've been training since I was a child, and yet ... Mother passed the year before my training was to begin. In losing her, I lost not just a mother, but a teacher. Mother used to smile and tell me, "Zelda, my love, all will be well in the end. You can do anything. But she was wrong. No matter how I try or how much time passes ...t he sealing power that is my birthright evades me. Tomorrow I journey with Link to the Spring of Power to train. But this, too, will end in failure. Such is my curse."
Page 7: "I had a dream last night ... In a place consumed by darkness, a lone woman gazed at me, haloed by blinding light. I sensed that she was ... not of this world. I don't know if she was a fairy or a goddess, but she was beautiful. Her lips spoke urgently, but her voice did not reach me. Would I have heard her if my power was awoken? Or was my dream simply a manifestation of my fears? I am sure I will know the answer soon, whether I wish to or not ..."
Page 8: "I turned 17 today. That means this is the day I will finally be allowed to train at the Spring of Wisdom. When Link arrives, we will set out for Mount Lanayru. The other Champions will accompany us there. I have not seen my father since he last scolded me. Things are too strained now ... I will meet with him when I return ...
"Actually, I've had a horrible feeling ever since that weird dream. No one would believe a failure of a princess, but ... Right now, for no particular reason, I am filled with a strange and terrible certainty that something awful is about to happen."
Pretty interesting stuff, if you're invested in Breath of the Wild's plot and characters.