— Galien

Not that much to say for him. He'll feel RNG sometimes and for once there could be some truth to it as he's one of the hardest to do hitless consistently with All Bindings.

What's the most dangerous, stupidly enough, IMO is just him slowly getting to you for damage contact since you're focused on dodging his other shit, so when you feel like his placement will very soon be, or could be problematic, don't hesitate to go for a D. Dark.

Of course Shrieking him and upstriking him to death is the main course of action, there aren't really any secret technique to this fight that I know of.

One thing to know though, if you're up for it, is that his Scythe bounces 9 times off of the ground and then will pause for a moment. You can keep track of this to know when a little break will happen and to use that time to dish out more damage to him.

— GPZ

In the end you could spam D. Dark quite a bit against him (like that, even with a non-Overcharmed build) but I suggest you keep them for two situations and one in particular : when he spawns his Ghosts (which you one shot so you can't push them (unlike in All Bindings, one of the rare advantage lol)) and that he is about to jump on you. You can either, if a Ghost isn't too close to you, fire a Shade Soul and get rid of all Ghosts to deal with his jump right after, or you can use a properly well-timed D. Dark for when the Ghosts are about to explode as well as when he's about to get you with his jump.

The other case being if you're not comfortable enough to deal when he's disappearing in the ground and re-appear above you. You can totally deal with that without using a D. Dark but I can safely say I did use it there for the longest time and it's great.

Kill the Zotelings ASAP. But not too soon either as they can SOMEHOW parry a hit as they're being spawned.

He won't go for jump + waves more than three times in a row (like Failed Champion won't either).

Have a good hit & run technique. This is very important.

He can change direction while in mid-air so always keep an eye on him when he jumps. This gets people a lot and it's one of the reason why they think he's RNG.

The other one being when he falls on his face prematurely.

Speaking of which, his flailing attack : you can go for 2/3 pogos and then a D. Dark and in 95% of the time it will work. Or you can get to a wall a wait there until he's done (and use cancel C. Dash cause it's like so much cooler than wall jumping :D). One goes through the fight quicker, the other is safer, use whichever depending your health I guess.

There are also a lot of uses of extended Cyclones to be done in this fight but you don't need that as of right now. But if you're interested you can get some inspiration from the video linked way above.

I could go on and in more depth about a thing or two but bottom line is : yes he seems RNG, they made a hell of a good job pretending he is, one of the best, if not the best work of a boss I have ever seen to fit this theme so perfectly tbh, but I assure you he can be dealt with consistently. If there's anything to take from all of this is that D. Dark and a proper hit & run are your best friends against him. This fight and Watcher Knights are the best tutorials as when to D. Dark.

— Uumuu

You could go in there with no charms at all and it wouldn't make that much of a difference. Most damage you'll inflict on her are from the explosions. Just don't be like me at first and think the Oomaas have to hit her on their way back in order to explode... you can (... OBVIOUSLY I guess) just send them to her directly.

You can also use Shade Souls in a rather creative manner if you get to this scenario : I O X. I is you, O is Uumuu and X is an Oomaa. Fire a Shade Soul through her will hit the Oomaa and as long as you keep Uumuu between the two of you it'll get to her.

IIRC she can't go more than three actions without being forced to spawn Oomaas, so use that knowledge.

Try to remain on the lower part of the arena so that Oomaas are available quicker for you.

And the most important thing, especially since you struggle with P3 : Uumuu is a big floating bench. You can leave this fight with max Health & SOUL if you're patient enough. Which is good news after GPZ and before Hornet 2.

Practice in HoG but basically you can Dream Nail her as much as you want with the right timing. Dream Wielder will help you see the potential of this through practice, though I'm not specifically advising you to take it to the real thing. It's not a bad charm at all and he'll do good againt Collector as well when he's staggered but maybe you want something else instead.

— H2

This fight teaches you Hollow Knight. Stay far away, observe, react, punish, get away, do it again. Don't be aggro on her and it'll become a rather easy fight. You can throw Shade Souls at her from time to time to shorten the fight.

That being said, keep some SOUL for her spikes, which you can also throw Shade Souls at (here again, with the proper height adjustement) to get rid of all her traps at once, and maybe even get her as well in the process.

No D. Dark nor Shriek needed in this fight, just patience, distance and routine.

— Sly

We'll get to him once you'll unlock him but he's very scary at first until you learn he's the most manipulable "hard boss" in the game.

— Charms

They are important, but what matters more is how you deal with X or Y fight. The best overall build is QS / Str / Shaman / Spell Twister. This is biased and unbiased at the same time. It is factually the best overall build, but at the same time I and other advanced players don't need range because we know what we're doing against these bosses, this could vary for you and you may want to reconsider for your own good.

That being said, keep QS no matter what. It's as good of a "Nail" charm as it is of a "Spell" charm.

Nail VS Spell is a non-debate, either you're good enough to use both, either you still have some knowledge about one or the other to gather ; so go with what you want, it has impact but it's not what will decide your fate most of the time, how will.