So, I bought the mega-events DLC and had a lot of fun with it, well, except for one thing. The artifact. I think the main problem is how it activates, and how other factions react, aka not at all. When I played, it activated for a faction that wasn't too powerful, but not weak either. They were also located on the other side of the map, and all their neighbors were at good terms with them. Once they amassed a fleet (which was easy due to the one ship one turn effect it has) they easily picked off their much larger neighbors one by one, the ones around them not really noticing what was happening, nor caring.
I did my best in trying to hold them off, but since nobody cared about the artifact obviously being a really, really bad sign, I could do little on my own but hold my ground. They were also seemingly immune to my massive influence, and planets conquered within their territory did not move the borders. In the end, I just found this more frustrating as my AI allies did nothing but joyfully make trading routes with them and being annoyed at me for fighting their "friends" before being eaten themselves. I stopped playing as it felt as the game had been hijacked by a cheater. I suppose it did work as a cynical story about the human condition, but that is never too fun to play.
I think the artifact needs to be reworked, and only appear for factions that really need it as a boost (about to lose, for example), or perhaps the purpose I thought it had; make a minor race act like a major.
I also feel allies should act more like allies, instead of glorified non-aggression pact factions. I help them in their time of need, but ignore me when I need their help. Together, we could have beaten this empire, but instead they were too busy serving themselves on a platter.