You've conquered all the divine beasts you have the master sword and you're thinking about fighting the final boss, And there's a few things you'll want to do first, this is the top five things you should do before fighting the final boss.
1. First thing you'll want to do is get stasis plus
The way you get this is you go to the Hateno Ancient Tech Lab
you'll want to talk to Purah and she'll say she can upgrade your runes you'll want to use ancient parts such as screws gears core shafts anything that you get from a guardian,
once you get stasis plus, it will become your most used rune when you have stasis plus you can freeze enemies and bosses not only is this super useful if you say need to heal or make a quick getaway but it also makes it so that you can do quite a bit of damage to you know that boss or enemy and it can't do anything to you so it's, it's a really nice thing to have.
2. The second thing you'll want to get is ancient gear
you're going to want to use the master sword to kill guardians once you have the master sword you can obliterate Guardians, you'll get lots of materials and you're going to need those materials for ancient armor and weapons.
that you've gone to the Accola engine tech lab right up here
You'll find a computer and you can talk to this computer and see all the recipes you'll want to craft,
all this because the armor gives you a significant damage resistance to guardians and the weapons do extra damage to Guardians
3. The third thing you'll really need to do before you take on the final boss is master parrying in dodging
this is absolutely necessary the final boss is nearly impossible, if you have not mastered pairing and dodging harrying is whenever there's a projectile coming towards you. You can pull out your shield and hid a if you time it just right you can deflect the projectile back at the enemy, you can literally kill guardians in one hit using this and dodging is when an enemy is attacking you and you dodge at just the right moment time will slow down, and you're able to start just dpsing whatever you're targeting.
4. Fourth thing you'll really want to do is kill some lynel
These guys are tough they might be harder than the actual final boss itself, but that's good because fighting Lynel will get you prepared and trained for anything you also want to learn, the fighting patterns of Lynel because there totally isn't to Lynel and the final dungeon the last thing, you'll really want to do is upgrade your armor, the way you do this is you want to find all four great faerie shrines hidden around iral, each one you find will increase the amount you can upgrade your gear, you'll need a lot of materials but it's worth it you can level up your armor it'll increase the defense give you special buffs it's really really good I highly suggest doing it.
5. Fifth Things you’ll really want to do is you need to have a wolf link with 20 hearts
this wolf link can summon Wolf Link as many times as you want. There is no limit and no timer. He will attack everything that is bigger than a squirrel. He will hunt for you, kill wildlife and enemies alike, and you can just pick up the meat and loot afterwards. He will also attack "hidden" enemies like Treasure Chest Octoroks and camouflaged Lizalfos you might have not seen yet, but be careful, Even if you wearing the Sheika armor and has a stealthy food buff, the chain on Wolf Links paw will make enough noise to alert enemies to your presence, chase critters and horses away and wake up sleeping Bokoblins. and It’s a wonderful thing to beat the final boss with your wolf link.
So those are the top five things you'll want to do before taking on the final boss, like I said some of them are necessary some of them you will highly want to do there are a few other things that you can do such as finding all the memories, for a secret ending find all the dragon shrines, because you can get all kinds of cool loot and materials from them you'll want to cook really high tier food, because when you take a heavy hit you're gonna want some food to heal up real fast.
You'll also want a really good horse I suggest heading to this area on the map and looking for horses it's really helpful when you have a horse that goes really fast has lots of stamina and doesn't die in one hit trust me on this, but there are a easy way to get a great horse, summon an epona by shop an Amiibo figure or amiibo nfc cards, the twilight princess link and SSB Link can also get Epona.
You'll really want to do is explore the world find everything you can find get as much gear as you can you want to be prepared for the final boss the last optional thing I suggest doing is doing the shrines you don't need to do all of them just get at least 15 hearts so now hopefully you're ready to take on the final boss I wish you luck hope you don't die.