Earth exists in the setting, but it is becoming burnt out, having been “used up” in efforts to achieve expansion in the galaxy. Few planets have the sorts of resources that Earth once had.

Earth has no gate or wormhole, the first being discovered by colonists arriving on Alpha Centauri Prime.

There are a number of types of non-human sapient beings. Below are just a few of them. Note that there are many “humanoid” species out there, but that these are all essentially humans who have been modified or have evolved over time. It appears that the builders may have spread human DNA around the galaxy at some point in the past.

Clouds of interdimensional gas, essentially, with floating occlusions of solid form (which they can move about interdimensionally), that form tusk-like solid protrusions from which the name is derived. They communicate through chemical emmanations.

To the extent that communications have been established with the Tuskegar, they have been a great boon to humanity, allowing advances in several technologies.

No homeworld has ever been found for these beings. Instead, all that remains of their culture are the gates, the building of which is what gives the builders their name. Though there is no clear homeworld there are many other sites built either in space or on planets that are of a similar age and technological level as the gates.

What happened to this culture is a mystery to be discovered in play. Many hypothesize that the Tuskegar were the builders, which seems a bit outlandish in some ways, unless you suppose that they intentionally evolved to become something that couldn't care less about their own ancient technology. Another notion is that humans were the builders, having left Earth at some point long ago in prehistory, though there is some pretty solid evidence that makes this, too, seem unlikely.

Below are some ideas the GM can use, but clever GMs will come up with a solution to the mystery that is both consistent with the facts, and yet fits their campaign well thematically.

The gates failed for some galactic-level reason, stranding all of their cultures, which were largely unable to survive the isolation. In this case it's possible that some few have survived on particularly habitable systems, remaining to be discovered.

In this case, the beings in question evolved to a higher level of existence, becoming energy or something else.

There are several species of Terran fauna that humans have uplifted to full sapience. Some of these have inhabited systems all on their own. Their origins, however, are clear. A common uplift trait is to have made them humanoid to some extent, though there are as many uplift types that are not humanoid as ones that are.

Uplifted Terran species include dolphins, octopuses, chimpanzees (bonobos), dogs, and crows which are only sapient in hive-mind flocks.

There have also been a couple of uplifted species found on other worlds.

There are multiple types of FTL drives, each serving various purposes.

There are two main methods of instantaneous transit over large distances.

Normal FTL drives can be modified to ensure survival of transit of naturally occurring wormholes. This is an expensive addition, and few craft have such modifications. More often smaller craft have to be carried by ferries specifically designed for such transit. But there are exceptions, typically military ships.

Worm holes are fairly common in high population inhabited systems, if only because systems without them tend to be relatively inaccessible.

Gates have been found created by the beings referred to as the Builders. Humans have not been able to replicate this technology (they have only just begun to understand how to activate these gates). Any craft (even those without any other FTL drives) can transit such a gate.

Even small craft may have FTL drives, but the fastest speed of any FTL drives is about 100 times C, meaning inter-system transit tends to take at least a fewq days if not weeks. However transit within individual systems tends to be pretty fast.

These drives vary in some specifics, but all have the following in common:

All such drives create a hyperspace bubble around the craft. This bubble places it out of contact with all normal space-time and matter, but energy can pass in and out of the bubble. Generally the larger the bubble, the more space-time distortion it causes, and the more energy it takes to fight that distortion. So smaller craft with smaller bubbles are faster than those with larger bubbles. In all cases, however, the fields are calibrated so that time inside and outside pass at the same rate relatively, avoiding the issues with moving at (faster than) relativistic speeds. Any miscalibration causes cataclysmic failure that makes everthing in the Hyperspace Bubble disappear completely (some people believe that such failyre causes the content of the bubble to move to another dimension, but nobody has returned from such a trip to confirm this).

As a side-effect of the hyperspace bubble, a shield can be created that absorbs a substantial amount of energy intersecting the horizon of the hyperspace bubble (in addition to the hyperspace bubble itself preventing interaction with all matter). The most common use of such shields are simply as protection from space radiation, but the military application allows ships to defend themselves against energy weapons, nuclear detonations, etc. Larger ships can generate larger shields, which can absorb more energy before overloading, and blowing out the generator.

Weapons forged in part from Archaeo-metal.