Mirrors

There are objects in this world that are highly overlooked by a number of lesser species which is mostly attributed to the fact that they not only lack the knowledge about the true nature of these objects but, they are also incapable of activating these hidden behaviours that the objects faciliatate and these objects are known as Mirrors although, it also includes any objects as reflective as mirrors.

Powers
The mirrors a method to actually travel between dimensions without the need for additional alien technology to facilitate this and so, makes dimensional travel so much easier as in some cases, it can be a hassle to get such technology just for that or an individual may be in a location in which they are unable to access such technology although, they may have access to a mirror instead.

While the mirrors allow dimensional travel, it actually takes the powers of an alien to activate this hidden property which it possesses with these aliens even being able to throw in people who aren't capable of activating the mirrors into the mirrors themselves which has led to a number of individuals going missing within the proximity of actual mirrors.

Limitations
Unfortunately, the laws of physics still apply unless, the alien is high enough to overcome these then, they may be able to do something about these effects with the laws of physics including the conservation of momentum so, an object going in at x speed will come out at that same speed.

Another limitation is the physical size of the mirror itself as an object cannot be inserted into a mirror if the entrypoint is smaller than, the actual object which has led to very large mirrors being needed for big operations or actual alien technology being used for these purposes instead.