This mod fixes the animation of the Horizontal Moonlight Slashes of the Moonlight Greatsword, allowing vertical aiming just like in ER and older games.
I do not know if this problem was fixed in big mods like Cinders or Convergence, so this will work only on Base Game, or with Mods that do not alter the Player Character Animations, i.e. c0000.anibnd.dcx file - since this mod alters it.

And just in case I'm also adding the individual Tae file too for any Modder/Modmaker that wants to look at it, or try incorporating it into their own Mod. Just make sure to credit me, ig.

PS.- Excuse the resolution of the attached Video, I'm working with what I've got.


INSTALLATION:
- Download the mod.
- Unzip the file and it will reveal to you a 'chr' folder and 'MLGS Tae only' folder.
- After Unpacking the Game with UXM, place the chr folder in a separate Mod Folder and use Mod Engine 2. (If you're new to modding, you can find tutorials on YouTube)
- Alternatively, you can place the chr folder in Game Directory - Or the c0000.anibnd.dcx file in the chr folder made with UXM. (Same thing). BEFORE REPLACING IT, however, make a copy of the original 'chr' or just 'c0000.anibnd.dcx file' file unpacked by UXM, in case you want to uninstall.
 - To locate your 'Dark Souls III' game folder, in your Steam Library, right click on Dark Souls III - in your game list on the left part of your screen -, select 'Manage' and then 'Browse Local Files'. It should open your browser at the exact location of your Dark Souls III folder - it's the one called 'DARK SOULS III' - INSIDE that folder you'll find a 'game' folder. This is where UXM will unpack the game. 
- At your Steam window, click the 'Steam' menu at the top left of your screen and select 'Go Offline'.
- Just in case don't close UXM. Usually its not needed beyond this point, still just in case your Moonlight Slashes should be fixed.
- If its not fixed, then click Patch in UXM and then it should work.
- Run the game.
- Enjoy.

UNINSTALL: 
Replace the c0000.anibnd.dcx file with the Original one that you made a backup of. 
Why you'd need to uninstall? Mainly if you want to play online, as animation changes can get you softban.

CAUTION:
 I have not tested this mod online, and it's quite probable that the game will either force you to play offline, or softban your Dark Souls account if you attempt to play online with this mod installed.
Sources seem to conflict now, with some saying its one of the most susceptible to get your account Banned, while others say that animation changes, atleast minor changes like this one are rarely a cause for Bans.
So if you go online, its at your own risk.
However, once you uninstall it, you can 99.9999% safely play online without any sort of penalty.