Longsword

Hello, sorry for my late response. That sadly isn't available in the current patch. But lets keep our hopes up for a future patch.

Implying there will ever be a future patch

Where can i find this Moonlight longsword?

Oh yeah, it was a good reskin, shame that they never used that chest on that Majula Mansion ever again.

Well, you can get it with cheat engine. And I heard that it's not bannable. But it's still a very shady method ofc.

Not really shady if you're just getting a reskin and nothing else.

But not available for those who only play offline.

sorry to bust your bubble 1 year later, but by asceting the Things Betwix Bonfire you can find falconer soldiers in the starting area, before the fire keeper's house. They drop sunlight medals, at a low rate. You can prevent them from despawing after 12 kills by joining the covenant of champions.

OR IF YOU PLAY OFFLINE JUST CHEAT ENGINE IT IN YOU PIRATE
(I recommend mrantifun's trainer for it has a built-in function which changes ID's of items, allowing you to turn an already existing weapon into the sun sword. or just get one sunlight medal and multiply it's count to 30)