The Weapon System of Lies of P

 It took me getting I think most of the way through the game (given that I've come around to fight a souped-up and more horrifying version of the first boss, like Iudex Gundyr from DSIII, but a mandatory fight) to wrap my head around how Lies of P's weapons work:

First off, boss weapons (as well as one I got for getting some "Premium Edition" version of the game) are an exception here: these are single-piece weapons that just are what they are.

But, the vast majority of the weapons you find in the game come in two parts - a "blade" and a handle.

The blades are the things you'll upgrade with various moonstones - starting with Hidden Moonstones, then Crescent, then Half, and finally, as a capstone, a Full Moonstone.

Handles, however, can be swapped between different weapons as you like. Each blade comes with a handle, but you are under no obligation to keep them attached to one another.

The handles don't need to be upgraded, but the handle essentially gives you the weapon's move-set. If you want a spear-like weapon that you can thrust repeatedly, you might get a handle from one of the spear-like weapons, but you can put a big ol' wrench head, an electric circular saw, or what-have-you on it.

The handles will also have stat-scaling, and can be altered to skew more toward one stat or another with various cranks you find in the game. For example, I have played most of the game with the Booster Glaive (both blade and handle) and used a crank to increase its scaling with Technique (though at this level I seem to sometime get equal if not better damage increases by bumping up my Motivity).

The other element at play here is your Fable Arts. As you fight, you'll gradually build up these blue bars under your stamina bar, I think starting with a maximum of 3, though upgrading your P-Organ with Quartz will eventually allow you to get more. I believe each blade and each handle comes with its own unique Fable Arts, which spend 1-3 of these charges for a powerful attack.

Again, it took me a while to actually figure this all out - upgrade materials are also not profoundly plentiful, so I haven't actually done a ton of experimenting (I've unlocked the ability to purchase unlimited Hidden and Crescent Moonstones - I'm hoping I can do so with Halves to get other blades up to +9).

Still, it does seem like I ought to try out some of the other handles with my now +10 booster glaive blade.