Present time: So, rebooted Makkari and Ajak are women (Makkari is actually a black woman... Marvel is so woke). Makkari lost all her senses and her telepathy as a result of an attempt to maintain mental contact with a Celestial.
One million years ago: Ajak on her own, but with one-sided prep, goes to face the Avengers of that time (which have been shown since Avengers #1): Odin, the Phoenix Force of that time, Starbrand (who is a Hulk-like being), Ghost Rider, their Sorcerer Supreme, their Iron Fist, and their version of Black Panther.
Before she finishes her speech, the Starbrand / Hulk-like creature throws two punches that seemed to destroy her face and to scatter molecules. She, then, uses a conduit that vents primal energies and that supposedly should hurt even Starbrand.
Odin reacts with lightning-charged strike with Mjolnir, that destroys her body even further. She, then, starts to reconstruct her body, and uses a device that starts collecting the data of the Avengers, while strikes them with "enormous death blasts".
Ajak recognizes Odin, Phoenix and the Hulk-like Starbrand as the most power of the Avengers, as Ajak has specialized in understanding beings of Cosmic Scale like that (she's the one who communicates with Celestials).
A punch from the Phoenix shatters her jaw, causing similar damage to the one caused by the Hulk-like creature.
Then, Ajak realizes that all other Avengers "of smaller strength" actually play on different scales. Their Iron Fist shatters more of her face, pre-historic Black Panther caves his fist through her chest with claws, and, then, pre-historic Ghost Rider finishes the job, "killing" her and scattering her molecules.
Ajak's mission was a success, as she gathered enough data and couldn't be really killed.
She is ressurrected and goes back to the Eternals, and says that the Avengers do not interfere with their plans, so, they don't need to annihilate them.
Back to present: female Makkari and Ajak find the new home of the Avengers (a dead Celestial body). Ajak is crazy, and claims it's a blasphemy that the Avengers carved holes inside her "beautiful" God. Ajak blasts omni-directional energy and orders the Avengers to eturn the Celestial to her.
Ghost Rider sees it and comes down to talk with her. Ajak is still crazy, but, when she is ready to strike, Makkari runs her 100 miles away.
Ajak and Makkari engage in a battle (nearly impossible to describe), but Ajak has clearly the upperhand. Makkari says that Ajak had no chance against the Avengers.
Ajak and Makkari are friends again.
Ajak states she made a mistake one million years ago, when she let the Avengers live.
It seems the Avengers and the Eternals are in for a clash.
As to my conclusions:
* the BC Avengers are EXACTLY the same line-up we have now. Jason Aaron has worked on them since #1.
* Phoenix, Odin and Starbrand seem to be in the same league powerwise.
* The Hulk-like Starbrand is described by Ajak as a "planetary defense system". She-Hulk had said the same circa Avengers #28 that the Starbrand was a planetary defense system "sorta like me". So, She-Hulk and the Starbrand are somehow linked.
We will have all these answers in Avengers #750 next month.