I am just going to list ways the ascension gate could be made.
A. It could be a physical Megastructure, powered by black holes ,supernovae ,or neutron stars.
B. It could be an artificially created wormhole
I was originally going to list more, but then I couldn’t think of any more
It could be a device creating such a massive force through time that it reverses the universe, with shields protecting your colonized - or allied, if you want - systems, although I don’t know what this would look like, maybe just a bunch of Dyson spheres/fusion reactors/antimatter reactors/zero point energy harvesters, connected to a tiny, bland sphere. I think it would be a funny end if you advance technology farther then anyone could imagine, and generate more energy than any civilization should ever need, just to make the most bland looking thing ever.
Here’s how it “actually” is (what I based the way it is right now in the game as a prototype):
Simple as that. And those properties lead very nicely to it being an end goal of the game by requiring researching all technology and collecting vast amounts of energy. Both of those goals give other space empires the chance to stop whoever is building the ascension gate which gives a nice bit of last conflict in a Thrive playthrough.
ok
It has to be 20 characters long so bla bla bla
Instead of replying “ok” and using post filler, which is against the rules, you can like a post or give it a 
i always pictured entering the ascension gate like this.
you would finish building and powering the ascension gate, the cutscene starts to play. hundreds of large passenger carrier ships line up in rows, almost resembling as though they might be going to war. the camera zooms in and flies through one of the window of the ship and peers out of the front window, along with several creatures (or the camera zooms in on an empty spot, like ship POV, regardless) you see ahead, a large rectangular structure, segmented in nature, blue (or other color) energy zaps along the frame, and the frame almost looks to break apart from the shere force of the energy rushing along it, and it separates. Quiet for about half a second or so before a bright bead of light blasts open in brilliant rays of light. you now see the siloets of the many space ships fly off to the center of the ascension gate. then credits roll or whatever.
Have you played the latest Thrive release all the way to the end? The ascension gate and the ascension cutscene is already in the game.
i finished the current game a couple days before my last post, i want sure if that was more or less a place holder animation of sorts, i assumed that because with a name like “ascension gate” and with the device being discussed as needing an extraordinary amount of power i had expected something more grandiose than what’s currently in the game. Is the current animation more or less what that cutscene might be like in the finished game?
Just placing a bunch of the dyson swarms wouldn’t be engaging gameplay at all, just annoying so you just need one in the prototype.
It’s pretty much structured exactly like I imagined it, but obviously the scene is quickly thrown together so that I didn’t need to find an artist to collaborate with / spend a lot of time tweaking the scene.
ok, i just mis-understood given the posts ive read then. I do wonder just how much power will be needed to power the gate though.
(I am the same Amir as the OP, but using a different account) I imagined it as a large gate-shaped megastructure. Like this image I found online
but much bigger, on the scale of a ringworld or something
and there would be spaceships flying into it
I imagined it as a large ring structure, with minimal thickness and length.
I previously had imagined it similiarly to @aah31415
But actually the way it is currently made in prototype endgame cutsene is quite good too for me. It feels like you are not ascending yourself with your ships, fleet or whatever you’ll bring, but only you and your body.
So ascension gate in such form only makes one god entity and the rest of your species stays here?
The first member to ascend can just use their powers to immediately ascend the rest of the species. Just make sure you trust Bob before letting him be the first one through the ascension gate.
I wonder how much a betrayed civ could do against a malevolent deity… perhaps they could manipulate it emotionally?