If you chose to fight him, remember, this was your choice. Good Luck.
The fight begins and after being pushed to your limits emotionally, you push your powers to their limits, fighting the very being who offers you a chance in a lifetime! To ascend into a greater being who could guide The Multiverse to great things you wanted!
But even with the combined might of all nine of you, you're only equally matched to Marduk or even not as powerful as him, who easily evades your attacks, frustrating you.
Then the battle starts taking you across Time, Space and The Multiverse; captivated by the many places you, your group and Marduk suddenly travel to, one strike after another with exchanges of throwing punches, tail swinging, beams streaking, blasts throwing, all at once!
All the while, you all retain your current forms: Marduk retaining his and you and your group retain your Beta Shapes. It is as spectacular as it is chaotic all in one. It finally took one hit from you or someone else on Marduk to give you a chance. Until now, you and your team tried to attack Marduk, but instead you attacked each other after each of his phases. But either you're stepping up a gear or he's letting you hit him at long last.
Considering he's going to die anyway, he starts glowing from his body, giving you his gift and in turn, giving another gift to everyone else. His shining body sparks across the rooms of his lair, deep beneath Demitra once you all return there and the present.
If you chose to race against Marduk, it's almost the same, except no fighting. And as you race against him, you travel back in time with him: To the creation of the very Multiverse itself. If he wins, you and the rest are destroyed. If you win, same as how you fight him: his body shines out and gives you the gift.
As you all are engulfed by the light, you emerge out in your Gold Shapes, just like with George, Hyacinth, Isaac and the rest. And, of all beings, Yuri Volodnikov himself, the man who discovered The Link, which he calls The Volodnikov Effect. The halos over your heads are The Gyro Keys and as you touch it, it becomes one for many purposes you intend to use.
You and your eight pals phase to Rhye and see the world completely destroyed. But you soon learn that it hasn't died for nothing. When you phase to any known worlds, you see the wreckage The Last Crusade left behind, many people who's lives were lost, those who survived and those who are displaced were catastrophic, but a lesson worth learning for years to come. Many of the FarSpringers on Rhye are back on their homeworlds and those who got separated are on worlds they'll have to temporarily settle until a solution can be found to go home to their worlds.
The people watch the now former FarSpringers and see the heroics acts they've performed against The Last Crusade and accepts them, thus allowing full support of the Roadmap: albeit delayed given the carnage. The FarSpringers (both formerly with The Link and currently with HoleCaster, get images in their heads, appearing to be schematics for the missing element to perfect WarpHoles).
The Eartheans' campaign is foiled and their powers stripped as Marduk expected, leading into "An Orgy Frenzy" where the remains of the Conglomerate devour or kill each other to reclaim their supremacy, only to be captured, killed or surrendered to the FarSpringers who use HoleCasters (since the WarpHoles created by the HoleCasters are not based on The Link).
Peter & Wendy reshaped back into their Zorcai forms, as does the others now that The Link fades away (they were in their human forms at the time of their last visit to their apartment) and happily co-exist with the Eartheans they've saved from the Conglomerate on Felocke, who will become a new world for the Eartheans to settle on and immediately ditch the ideas from the Conglomerate.
Unfortunately: The Talrrusan Republic is in tatters, as Encrantei was nearly ruined by The Last Crusade, Cecil going into a catatonic state, leaving Bobbi as the new Prime Minister, since she was taught by Cecil prior, simultaneously looking after Cecil for the next six months till his self-exile to Kalandra for a full year.
Over Herph, you see a large spacecraft that seems to originate from Vela. You send the coordinates and ship to the Guild wherever they may be to send an expedition there to investigate.
On Knowhere, the experiments the Eartheans were conducting were the MoleFolk (captured Kalandriks during The FarWar) were placed in Cryotubes, awaiting to awaken and rule The Multiverse based on the Conglomerate's programming, along with the Morthrens, weapons of mass destruction based on Jincillan Technology. But, as you use your Gyro Key to destroy the programming by their creators and phase the Morthrens to Jincilla Two, the Jincillans absorb the Morthrens into them, destroy the virus and expand the world greatly, leaving only the MoleFolk to decide on their own as they awaken on Knowhere.
You then phase to Demitra's surface, letting the Demitrans know that the Multiverse is open to them and offers them passage to the known worlds so far. Marduk's Lair is still active, but has now moved to Knowhere as the secret home of the KeyMasters, reshaping the interiors formerly built by the Eartheans to conduct their experiments.
Ultimately, you return to the worlds you know throughout your life: Orum and Nuorum. Although Orum is still too late to be saved, the fragments of it are still worth using, including Ravenscroft, the base you and Azaar were sent from as it becomes sustainable inside to provide life support. Other fragments should also be considered like a memorial dedicated to those lost by The Great Accident. And lastly Nuorum, where Nikolai learns from the Andertons to become a great leader and turn Nuorum into a superpower greater than both the Eartheans and Kalandriks and now on par with both the Demitrans and Talrrusans (eventually). You smile at him in your incorporeal form, watching him improve himself and promising things to come. You couldn't be anymore proud of him, having watched him change from delusional to enlightened. But before you could meet him; you visit Jorja one more time and see the place once occupied by you and decide to bring in two humans to look after the place.
And as his day is done, and his duty shall call in another time, Nikolai returns home, only for you to hug him, getting him to turn towards you in your new form.
Hi, Nik. How are you?