Yeah I remember the first time I tried using one years back in the "original" Space Rangers 2. Except I remember getting it as a reward from a quest very early on - it didn't have much charge but it did when I finally decided to test it. Actually I didn't know you could find one with that much charge already, I always thought you find them empty and then have to wait till they charge up...

I say "kind of" surprised because by the time I'd used it I had already talked to enough Kelleroids (prior to launching software), so it's not that hard to work out if you're into the game a bit. Also I'd say this is one part of the game where the translation itself isn't the problem - vague though it may be.

Naturally at the stage of the game you're likely at (I'm assuming you started as a human and started probing planets early?) it might be a bit crazy to use. One of it's common uses originally was to bring lots of things to kill to you for experience points.

Better uses exist however - it's really good fun to launch this amidst opposing dominators (especially if you're disguised as one of the Dominator sides that's fighting). It's also useful for helping to soften up pirate systems prior to taking them on.

Game clearly states during briefing what kind of habit each dominator boss exhibits.
Plus, scientific base regularly talks about it when accepts dominator remains.

Main use of this artefact is to call dominators and either capture weakened system (which they left) or let them weaken defenders of system you called them into. Getting exp is an unintended side effect, and it is the reason of added illness after usage. In early versions it didn't exist.

Problem is, the Transfactor Beacon description says nothing about the Dominators; I thought it was a tool to summon your own researchers or something like that. I just couldn't fathom an artifact like that being found on MERCURY of all places.

You'll notice though that the artifact is a kelleroid artifact (unless I'm mistaken or something has changed since I last played this) - although this may not be obvious if you're not that familiar with the game.

So it makes sense that a kelleroid artifact would call kelleroids (though other dominators can intercept the signal and also appear).

Artifacts have a "manufacturing race" just like weapons and equipment.

As for where it's found - artifacts are randomly placed, so it's probably best not to think about it too deeply. ;) That said, maybe it was being transported back to Earth by a previous ranger, who then was destroyed by pirates near Mercury? That's apparently where all the other crap that's found on the surfaces of planets comes from - stuff that's from destroyed ships or jettisoned from ships.

Game regularly says about differences between dominator races, iirc during briefing you hear it first time, and states in plain text that Kelleroid is a most advanced boss (only one with blackhole drive), which studies galaxy.