I'll reply to everyone when I can, busy trying to get my car repaired.
To quickly answer you though, I sent an email and a msg on Msgr, I'm... simply waiting at this point for a response.
atm I can just tell you what I know and allowed to reveal... (gonna make it as spoiler-free possible)
1. The "Cosmic Rival" is considered an "unnaturally" born cosmic being, born of
the actions of the Phoenix Force and
a particular Mutant.
2. This new being has powers deemed "transcendent" due to the fact it possesses powers the Cosmic Collective (beings such as Silver Surfer, Galactus, the Beyonder, the Phoenix Force, Death, Oblivion, Eternity, etc.) has declared "unnatural" and something that "should not be". This makes the newborn Cosmic Entity the only "Cosmic Outcast".
3. The Cosmic Rival however does have support, which comprises of a very shady and dangerous occult, and various Mutants (like Magneto) across the galaxy, who deem this being a "savior" and "liberator". The Entity goes on to become a "Cosmic Rebel" of a quite indiscernible cause.
4. Fear of what the Cosmic Rival is capable of without any real means to control it, causes much enmity from the Cosmic Collective, and particularly from the Phoenix Force itself. Being rejected, made an outcast, and having so many elements to go against, stirs immense bitterness, anger and rebellion from the Cosmic Entity. Thus begins an epic rivalry between the Phoenix Force, and the wayward "Cosmic Bastard" as "someone" describes it.
5. There's one particular power that the Phoenix Force and Cosmic Rival share, however within the Cosmic Rival, this power evolves into something that terrifies and even threatens the Cosmic Collective. It is decided by the Phoenix that the "Bastard of the Cosmos" and it's One True Host, must be destroyed. Problem however... due to the progression of these arcs, a powerful foe rises that cannot be challenged, and he threatens not just the main timeline universe, but the Multiverse as well. This villain is a fan fave and I'm glad he's getting his spotlight, but I can't reveal who he is. After the rise of (cosmic super-villain), the Phoenix and Cosmic Collective find the ONLY thing that could defeat him... IS this Cosmic Rival. And the scary decision has to be made... should they kill the Cosmic Rival so it would never be a threat to them... but now have to face a battle they know they can't win... OR, allow the Cosmic Rival to be, so it can defeat (cosmic super-villain) but now run the risk of the Cosmic Rival evolving into something irreversible, and now face "changes in existence" as they know and protect it...
That's what I have, I'm sure the writer would be willing to share more of this X-Men/Avengers story