Space Dust
Space Dust? ‘Tis the scourge of the space-ways, it is. Not because it affects any Galactic species that still operates in this plane of existence, because Space Dust doesn’t. It really is just made up of regular interstellar dust particles that have been collected until there’s enough to be worth selling to a member of the Precursor species. The species who have theoretically transcended this plane of existence, in other words — but yet now find that Space Dust is the most absolutely, completely, and reverse transcendentally amazing high in any plane of existence.
Not every Precursor is a Space Dust junkie, thank whatever deity you prefer. Which is why they all don’t keep coming back to our plane of existence in order to snort their way through the Empty Dark. But a few do come through, from time to time — and they will absolutely give us lesser beings all sorts of goodies in exchange for a briefcase full of the stuff. And the Precursors will pay for Space Dust. They’ll pay through the noses that many of them never even had in the first place for it.
As you might imagine, the Galactic Patrol has views about letting criminal lowlife (and garishly dressed) scum make far too-profitable deals with drug-crazed Precursors. They are usually in a position to arrest Space Dust pushers for something; naturally, the pushers routinely object to this, and typically forcefully. Fortunately, the Precursors rarely actually give their drug dealers ultra-tech weaponry. Unfortunately, the Precursors routinely give their drug dealers things that can be easily traded for top of the line, black market military tech. All of which can make raiding a Space Dust pusher facility a tricky prospect, but then the Galactic Patrol is there to do the tricky jobs.
Now I’m imagining ancient gods as strung out junkies. They had all the vices of their times, why not: A Drug-War in Heaven? Entire cult-cartels? Lacing offerings with X to get new demi-deities hooked?