This page offers a guide on how to get through Hyrule Castle to reach Calamity Ganon.
Main Quest: Destroy Ganon
It is time for the final fight! First, we need to actually get to Hyrule Castle. It can be very difficult due to all of the Guardians swarming around the area, but the fastest way to approach is either from Wasteland Stable or Central Tower (of course you can approach it from a million different ways) as that will let you get straight to the town ruin’s Central Square and open the gates to Hyrule Castle. If you desire a safer way with less Guardians, approach from the north from the Woodland Tower. Or, get crazy and find some way to exploit the physics engine. It’s totally up to you.
We approached from Wasteland Stable and traveled along the footpath towards the castle following the path highlighted in the image above. If you are journeying at night, beware that spawning skeletons can become a huge nuisance if you are in the middle of sparring a Guardian.
Hyrule Castle Town Ruins
Hyrule Castle is surrounded by what used to be a lively town. Now it is in ruins and is swarmed by guardians and Ganon goop. If you see any eyes feel free to destroy them so that you can unblock all the stairs leading up to the Central Square.
There are Guardian Stalkers distributed fairly evenly around the ruins. They seem like they are stationary since they are resting on the ground, but once you get close they will stand up and start trying to shoot at you.
Central Square is marked by a broken fountain. From here, it’s a straight shot to the castle.
There are Guardian Scouts that constantly patrol along the bridge leading up to the gates. Run down the bridge weaving around their spotlights (or shoot them with Ancient Arrows if you have any to spare) and as you get close to the gate, you will witness a cutscene showcasing Calamity Ganon. You will also see the golden light that is Zelda.
Open up the gates using Magnesis to gain access to the final dungeon of the game, Hyrule Castle.
The Hyrule Castle dungeon is extremely elaborate and complex, with many side activities, enemies, and side content to be found within. However, if your goal is merely to destroy Ganon, there is a way to bypass all of the dangers that come with the castle and get straight to the Sanctum where Ganon awaits us.
As you run up the path, avoiding or defeating the stationary Guardian on the left side, you will find a waterfall. Equip your Zora Armor and ride up the waterfall.
Paraglide down and follow the river up to the next waterfall. Avoid or defeat the Guardian to your far left, and then ride up the waterfall. Paraglide straight forward into the next waterfall. Do not waver left or right.
Ride up that waterfall and you will finally Paraglide above what looks like a natural tunnel formation. Climb up the rocks and you will now stand on a path leading you straight into the Sanctum. There are more Guardian Scouts flying around the path so weave around their spotlights.
If any of your Champion abilities are on recharge, especially Mipha’s Grace and Daruk’s Protection, consider waiting in front of the Sanctum for everything to recharge.
For those curious, our initial loadout for the boss fight included the Master Sword, a Savage Lynel Bow, and a Knight’s Shield. The Master Sword will be at 60 power when fighting Ganon and the Savage Lynel Bow can fire three arrows but only consume one. We had a grand total of thirteen hearts and one wheel of stamina.