cosmic horror campaign

Hey guys, I’m a GM trying to set up a very unconventional cosmic horror game for five players.  And I need some pictures of gods and abominations to use. Any suggestions for interesting godlike entities for the characters to meet are also welcome.
Here’s the situation.
For about a year now my players have been bopping about in a homebrew space opera setting that they had asked for. The galaxy they mess around it follows the classic space opera clichés with the rippoffs of empires, federations, the Culture, ancient races, space bugs, humanoid aliens, precursors, technologic ascension to “higher dimensions”, and such. It has the same themes as most “progressive” scifi: things are getting better, technologic advancement is a positive, and people have hope for the future.  The players have enjoyed it but two were never really loved that type of scifi in the first place and they have had all the adventures the party really can have in this particular setting without repeating any story elements. So those two asked that we have a cosmic horror setting to change things up. But I said that I wanted to run one last campaign in this setting.
I always thought that it might be hard to really get into a cosmic horror storyline unless you have some investment in the world that is going to be destroyed.  So I am going set the story in the galaxy they have come to know so well. I am going to take those themes of hope and progress and shit all over them. I am going to destroy the universe that they have invested themselves in and though they will be able to influence almost everything that is going to happen to determine how their universe will die, in the end it will die.  The PCs themselves will have opportunities to survive the whole ordeal but as time goes on the setting will become unrecognizable.
Here is the background for their entire multiverse thingy. It came into existence after our universe faded away. The previous universe was the real world, there was never any way to travel faster than the speed of light, no psychic powers, no ascension, no technologic singularity, quantum computing turned out to be shit, and no free energy. Humanity still conquered the universe, but it took them 58 billion years to do it with relativistic spacecraft, and they never knew that they had actually conquered all of it since the universe was finite but unbounded. They essentially just circled back on themselves. Each stellar system was a state of its own unless other stars were very close. In those cases bloody wars were fought and entire systems laid to waste over millennia of slow attrition. And eventually all the stars burnt out, all the black holes withered away, all matter disintegrated, and humanity prepared to die alone in the darkness. But as the universe ended the physical laws began to break down. A kind of mania gripped humanity as it died and they started to destroy themselves. As this happened monstrous supernatural beings manifested throughout the universe and devoured huge swathes of mankind, destroying the fabric of reality wherever they went until the universe was completely unmade.
But that was not the end. Because supernatural forces actually existed, all the human Gods existed in one form or another, and humans actually had souls. But as per Abrahamic and Chinese tradition the soul is not the same as the mind, it is this crazy supernatural thing attached to the mind and body. So essentially in death human souls are little gods slightly less powerful than a Greek Daemon. And the uncounted quadrillions of humanity that had lived and died through the ages continued existing in the land of the dead. Here some souls serve gods while others do their own thing. The shapes they take are diverse and can be beautiful or hideous but all instill a sense of dread in those that face them.  The things that had burst forth from beyond space and time were the dead of countless generations. The physical laws had broken down enough for them to rip their way into the physical world. And no longer separated from the physical by the veil they could exact far more control over it.
Now it is time for the new multiverse created after the old universe’s destruction to come to an end. The humans seemed to have had some small influence in the how the new universe was made, so many things they always dreamed of achieving were physically possible. This also explains stuff like the unusual number of humanoids in the setting; the laws of the universe were manipulated in such a way that they produced humanoids. But this wasn’t done to help the people the new universe; it was done to make the torture all the greater when they had it torn away from them. They have bodies and minds but no souls. The only life descended from Homo sapiens sapiens has souls, and there is no reason why other than to impress upon everyone else how cruel, uncaring, and arbitrary the gods are. They have all these technologic accomplishments that will mean nothing as the laws they manipulate to create that technology cease to function. And all that hope for the future, that the universe can be made into a kind and loving environment is revealed to be a hopeless farce.
There are three plothooks to get the players into the scenario. One is series of catastrophes like novae in inhabited star systems. The appearance of beings fleeing other universes or the planes they ascended to. And the sightings of strange beings that cannot be recorded and are being written off as hallucinations, which physical examinations of the witnesses supports, but the similarity of the descriptions makes that seem unlikely.
I want to make the supernatural phenomena really hard to observe for the first few sessions. Physical manifestations of supernatural phenomena are alterations of causality and will always appear to be natural phenomena. Basically any miracle caused by anything would be due to the supernatural altering all the universe’s past, present and future resulting in alterations of causality and natural phenomena that would always appear to have a route cause in natural phenomena. So for example if a star suddenly exploded unexpectedly due to the action of the supernatural it would like it was always supposed to have exploded at that time and people just stupidly overlooked that, even if that seems incredibly unlikely that they would do so.
These limitations on how the supernatural appears to physical observers will be reduced as the natural laws begin the break down as the sessions go on. First things like the undetectable alteration of causality will occur, such as meetings with the supernatural always appearing to be hallucinations. Then single entities will begin to breach reality and manifest in the physical world for a short period of time. Until the stars are right and the limitless armies of the void flood into reality to devourer everything.
Regardless how they decide to pursue the opening eventually they will be contacted by beings referring to themselves as the Herlads. At it will become obvious that these beings are somehow involved with traditional that should be easily preventable for civilizations this advanced. These being will give people warnings about deaths they cannot prevent. Everyone who sees them will experience abject terror regardless of how intelligent, materialistic, or religiously devout they are. Technology that utilizes faster than light processes will fail in their presence. Wounds will appear on those contacted which do not heal, or are healed then reappear only for those that treated the wound to say that they did not in the first place. And no physical evidence will remain of the manifestation.

These beings will turn out to be ghosts, psychopomps, Mothmen, and angels of death who by their nature are heralds the end of the universe.