The God Marduk is a very confident and prideful God of the children of Enki. Being descended from the great God, he is very proud of his lineage, more so because his parents are also rulers of the Gods as well. So when it was time for them to gain control over their pantheon, he had lead the charge against Abzu and Tiamat.
He and his brethren had great ambitions to rise in power and gain respect from all the others divine beings of the other pantheons. And defeating and taking the rule from a Primordial is a great fear which is sure to grant him respect and fear from the others.
So when it came the time to fight against Abzu, he alongside the other members of his pantheon, led the charge against the primordial God. And with their combined might and help from his parents and his own power, he managed to slay the God.
Granted it was a hard fought battle, he didn't expect anything less from a being of such might and status and that is why he was so excited about it. He is a warrior as well and enjoyed a good battle and battling a Primordial is sure to help him gain more experience in using his powers and growing stronger as well.
In fact he is sure that he had grown stronger after the siege on Abzu. After they had defeated and killed the God, they took some moments to rest, though they had believed that they would be attacked by Tiamat since they had killed her husband and brother, she didn't.
They didn't know the reason why, but they were grateful for it as they were tired from the battle, though he was more than ready to fight against her as well. But considering the fact that she is the Mother of Creation, the others had far more reservations about attacking her.
But Marduk was different as he wanted to fight against her and defeat her and show his might to all. So he would train to fight and defeat her, which is when the other Gods would come to him and ask him to lead the charge against her. From what he understood, they chose him because of how he had fought against Abzu and wanted him to lead them.
But he didn't want to just fight and defeat her and so gave them the condition that if he led the charge against Tiamat and defeated her, then he would become the king of their pantheon.
And they had agreed to it, most likely due to his own strength which was much greater than the rest of his generation and the fact that he is the child of the direct line and rulers of the gods aside from Abzu and Tiamat.
And with that they led the attack against Tiamat, but it was far difficult than with Abzu as she had fought against them with more ferocity and beastial nature than the much more calmer Abzu. Not to mention the fact that she had created demonic beasts to fight against them in an endless wave.
With her great powers she kept on creating beasts to fight against the gods while she also attacked them as well. But when they started to gain more ground she pushed her back using her powers and went inside her home, from which more monsters appeared to fight them.
He mowed them down mercilessly as more and more monsters appeared in an endless wave against them but he wasn't deterred and kept on fighting to defeat the monsters and claim his kill. Then for some reason the amount of monsters coming out of the goddess' home increased and they fought with more power.
He felt her use more power as he could feel it but he couldn't know what as he was still dealing with the horde. Despite them not having the strength to defeat him, their numbers however was an annoyance as there was just too many beasts to slay.
On any other time he would be more than happy to do so, but due to the circumstances and due to the fact that Tiamat is the one he wants to kill, he fought with more prejudice as he kept on killing the enemies.
Soon, he had managed to kill enough that he would be able to fight her as he charged her home and saw her in a more demonic form. He was surprised when he saw her as he hadn't expected her to look like that when he went there.
Of course, that didn't matter to him much as he used his entire powers and fought against her. He smiled as he remembered how his axe had cleaved through her monsters she was making while he dodged and destroyed her attacks. He also remembered how she had cried when he chopped off her wings.
Then he slowly and quickly slashed and cut the rest of her body as she screamed and attacked him and though she managed to get a few hits in, he would be able to dodge most of the attack. And then after he had damaged her enough, he charged her with his axe and with a powerful attack, he chopped her head clean off of her body.
He watched as her headless body plopped down on the ground in front of him as he stood victoriously in front of it, and despite her immense size which dwarfed his own, he had managed to kill her all on his own. The rest of the Gods also came and seeing it they praised and congratulated him.
He basked in their praise and then collected the body parts except for her head which he had given to his parents. They had disposed of it as they didn't feel the need to keep it, and then he had used the rest of the body of the goddess Tiamat to create a part of their pantheon.
He used her body to create the land, sky and sea and put them under his dominion as he was very proud of it and made it just castle from where he would rule the rest of the pantheon. He had been crowned king after that and he was living his life happily as the king of his pantheon, as his own parents didn't have much of an objection to his rise to power.
He would bask in the praise and awe of the other Gods and would be attended to by the various women in his pantheon, the goddesses would gaze at him with love and admiration, and even Ishtar was drawn to him. And having the attention of the Queen of Heaven is a great achievement.
So he was very confused when he was chilling at his room as he was gazing at the sky he had made when he felt a small pulse of a two different powers, something which he was familiar with as his eyes widened.
'Is that... Abzu's and Tiamat's?' Marduk thought to himself as his eyes widened.
He took a few seconds to process that energy and then his eyes glowed with power as he snarled as he felt anger course through him as the palace shook from his aura as the servants working in it were shaken while other Gods felt his power as they looked at the castle in curiosity.
Of course there were others who had felt her aura, mainly being Marduk's parents and some of the more powerful God's had also felt it as well.
While at the marriage, GOD smiled as he watched the proceedings of the marriage between them. It not only served to make his children happy, but also made sure to make some ties between his children and the children of Chaos.
He looked at Abzu and Olorun as they were also looking at him. Abzu gave him a respectful nod while Olorun just smiled towards him with a humorous face as GOD also smiled at that as well.
'Hmm, it looks like Marduk has noticed her and Abzu's power. Well, I shall take care of it, can't have my children's marriage to be ruined.' GOD thought to himself as he smiled gently and snapped his fingers as his hand glowed for a second.