What Do The Sandman's Tools Actually Do?
Morpheus (Tom Sturridge) is a cosmic figure of many names. To his siblings, he is Dream of the Endless. To his subjects, he is the Lord of Dreams. To the queen he imprisoned in Hell for choosing the safety of her citizens over his affections (yes, that's literally a thing he did), he's Kai'ckul. To fans of Neil Gaiman's creative retelling of the original DC comic, he's the titular "Sandman." Regardless of the terminology, he's a powerful being, capable of b great deeds. Not necessarily good, sometimes even terrible, but undeniably great.
And that's in no small part thanks to his items of power — the Dream Sand, the Helmet of Dreams, and the Dreamstone. While not the most imaginatively named magical items on the market, Morpheus' toys mean business and allow him to interact with the universe in a way that mere mortals could never sufficiently comprehend or control. Here's a quick rundown of what of the Lord of Dreams' tools do.
Morpheus' Dream Sand is how he interfaces with his power set
When all is set to order, Morpheus possesses three items of power. Firstly, there's the Dream Sand, which he keeps in a small pouch, which probably throws everyone off, considering how his supply of Dream Sand never ends. Morpheus uses the sand to create dreams, or fulfill wishes, or even put mortals to sleep. Morpheus also uses the sand to travel between realms (kind of like Floo Powder, just without the irksome chance of saying the wrong name and mucking it all up). Should a mortal try to wield the sand, however, the results would be disastrous. While still powerful, the magic the sand contains is addictive and destructive to mortals, something every iteration of the story takes great pains to mention.
In short, the Dream Sand is how Morpheus interfaces with the bulk of his powers. While he is still a powerful Endless being without it, Morpheus needs it like a wizard needs a wand. It's a conduit for his abilities. Is that enough "Harry Potter" references? Okay. Let's move on to that rad helmet.
Morpheus' Helmet of Dreams is his symbol of power
Morpheus' Helmet of Dreams is his symbol of office. If the sand is his scepter, the helm is his crown. It also serves as his sigil by which the other Endless can recognize or call upon him. Unlike the Dream Sand, it's not inherently something that has powers, but it does seem to possess some of Morpheus' essence, as he considers himself weaker without it.
Horrifyingly, the Lord of Dreams created the helmet out of the bones of a dead god. Now ... he never elaborates as to who that dead god was, nor if the god in question was dead when the bones were acquired. That's for Morpheus to know and everyone else to agonize over. On a lighter note, the whole thing is a visual homage to the original version of the DC property that existed before Neil Gaiman recreated the story. The older version of DC's Sandman, a more conventional superhero, literally used a gas mask and sleeping gas against his enemies, and was just some dude named Wesley Dodds. Yeah, angsty gods are cooler.
So what does the Helmet of Dreams do, exactly? Well, it makes Morpheus feel good, mostly, and isn't that enough?
Morpheus' Dreamstone is a power reserve ... probably?
Morpheus' ruby, the Dreamstone, is the hardest item to explain. It's notably filled with the Lord of Dream's power, his very essence, but the why is a little vague. Suffice to say, whomever possesses the ruby possesses most of Morpheus' power. With it, the wielder can shape the very fabric of reality. John Dee (David Thewlis) does that very thing, and a lot of people die because of it.
Again, it's confusing, because the Dreamstone is never really said to have inherent power outside of what Morpheus imbues it with. Why did he need it? Why couldn't he just keep that power inside of himself? It's unclear, but it's possible that he needed it as a separate, unique conduit for his strongest abilities. The Dream Sand creates life and opens doors, but the ruby controls the space in which those things exist. In terms of destructive power, that's a sword versus a nuclear bomb. But apparently, Morpheus doesn't need it all that much, considering what happens in the wake of the John Dee incident.