Maya can never be supreme as it operates only in Vyavaharik level. According to Advaita there are three levels of reality:
1) Paramarthika Satyam
2) Vyavaharik Satyam
3) Pratibhasik Satyam
This is the absolute reality. In this level neither Ishwara nor Maya exists. Only Brahman exists in Sat-Chit-Aananda Swarupa. Here Sat means pure existence of Brahman, Chit means pure consciousness of Brahman and Aananda means infinite blissfull state of Brahman. There is neither any creation nor any destruction in this state. Just Brahman exists in Satchitaananda form.
This type of reality is called Ishwara Shristi. This is the reality at that level when universe is covered by Maya of Ishwara. Maya is the potential energy of Ishwara. For eg. We see Mirage in desert. That is illusion. We know it but we can't remove it by knowing it. We can just understand that it is illusion. Similar is the level of Vyavaharika Satyam. We can only understand Maya of Ishwara.
This type of reality is also known as Jeeva Shristi. We ourselves create these types of reality in our mind. For eg. In our dreams. Dream world is created by ourselves. Another example is seeing rope as snake in dim light. These type of illusions are instantaneously removed after knowing the truth. But illusions of Vyavaharik level can't be removed,we can only understand it (ie. Mirage still exists even if we have knowledge that it is an illusion)
Ishwara himselfs creates this Universe by the power of Maya. Ishwara does so because creating is his nature. Ishwara is neither inside the creation nor outside the creation but Ishwara is itself creation. Ishwara creates with the help of Maya. Maya has two powers.
1) Aavaran Shakti
2) Vikshepa Shakti
This is the covering power of Maya. By this power the beings in creation forget that they are 'Brahman'.
This is the projecting power. By this power the universe which we see is projected in this way we see and observe.
Is Ishwara under influence of Maya ?
No, Ishwara is not under influence of Maya. Although Ishwara is Saguna and saguna form is taken by the help of Maya. But still the nature of Ishwara is defined as Sarvagya (ie. All knowing). Hence Ishwara isn't deluded. But he uses Maya power to be in Saguna form and for creation.
How Ishwara creates ?
Creation is the innate nature of Ishwara. As Taittariya Upanishad says
2.6.1 He (the Self) wished, “Let me be many, let me be born. He undertook a deliberation. Having deliberated, he created all this that exists. That (Brahman), having created (that), entered into that very thing. And having entered there, It became the formed and the formless, the defined and the undefined.."
So he wished and he became many. So he himself is the creation. So everything in this Vyavaharik level (including ourselves) which we see is simply Ishwara himself.
What is the origin of Maya?
Maya is due to Vaasanas (desires) which are accumulated in the mind. How desires originated ? Desires are originated because it is originating now. It is seen through 'Pratakshya Pramanam' ie. Direct Perception. We can't trace first origin of it. But it originated because it caused Maya and Maya caused Ishwara Shristi. And as we can see Ishwara Shristi right now here, thus it originated. As we can't trace first origin of vasaana and hence we can't also trace origin of Maya. And Hence Maya is called to be existing from beginning. But it isn't in Paramarthika level.
How we got individuality ?
In Paramarthika level there is no individuality as only Brahman in Satchidananda Swarup exists there. But in Vyavaharik level we see individuality. As Vyavaharik level is due to Maya of Ishwara. Hence it is responsible for our individuality. As Upanishads declare 'he became many...'. Thus at this time individuality arose due to Aavaran(covering) power of Maya. It is described as Akash GhatAkash Vaad. Here Aakash is infinite and Ghat akash means part inside infinite. Due to influence of Maya a small portion called Ghat-Akash is covered by Mind Intellect and other sheath to satisfy it's desire (called vaasanas). Individuality arises at this stage.
Standard analogy example:
The standard example given to represent creation in Advaita is dream world. We see dream due to unsatisfied desires remained as impressions in our mind which are called Vasanas. Due to Nidra Shakti (analogous to Maya Shakti) we see dream and due to Vikshepa(projecting power) we create a new dream world. Just as Ishwara creates this world by himself (multiplying). Due to Anavaran (covering) power of Nidra shakti (ie. Maya) we forget we are dreaming and as we ourselves are also in dream world and now we began to think world and us as separate. This process continues until we possesses sharp intellect with Jnanam. Thus creation by Ishwara is analogous to our creation of dream world.
Mokshya in Advaita is not like other philosophies like Visishistadvaita, Dvaita and other where a Jeeva goes to Kailash/ Vaikuntha and enjoys with Lord there. In Advaita everyone is already 'Nitya Jeevan Mukta' ie. Already Liberated itself. Only knowledge is required to know this. When he gets knowledge he gets liberated immediately instantaneously (in the same way darkness is instantaneously removed from candle. ) A Jeevan mukta may also do not have knowledge that he got liberated. He is in the SthitPragya State as described by Lord Krishna in Gita ie. possesses no desire, nor gratified by Stuti nor angry by insult, neither laughs nor cries,etc...
He may go on doing normal activity inside body to destroy Prarabdha karamas. But he is not affected by such Karmas as he knows he is not that body, mind and intellect but he is the Supreme Sat-Chidananda-Brahman.
What happens after death?
There is no meaning of death here. It is just casting of Sthula Sarira. As he don't possess desire he isn't attracted to have any new Sharira/body. So he don't have rebirth. He is in the highest blissfull state so he doesn't desire to do any other thing or to get reborn in Samsara or other.
Even the Gods can't prevent him from doing anything as he is the self of everything(ie. Even God's also) as Brihadaranyaka Upanishad says:
1.4.10 And to this day whoever in like manner knows It as, ‘I am Brahman’, becomes all this (universe). Even the gods cannot prevail against him, for he becomes their self.
But he rarely chooses to do anything as he is in the most blissful state. So anything he does is of lower bliss than that state. But he may also, as Suka in Mahabharat did so one time. He pronounces 'Bho' and entire universe pronounced 'Bho' as he had became self of all. He did it to calm grieving Veda Vyas.
Meanwhile, the righteous-souled Suka, who had entered the elements, had become their soul and acquired omnipresence, answered his sire by uttering the monosyllable Bho in the form of an echo. At this, the entire universe of mobile and immobile creatures, uttering the monosyllable Bho, echoed the answer of Suka. (Shanti Parva chapter 320)
Thus for other people after moksha also he gets individuality as moksha/liberation can happen while being in Sarira also. But for him there is no individuality as he donot identify himself as body, mind and intellect. After death also sheath of mind and intellect are there. But he may choose only to live in Paramarthika level by casting off mind and intellect thus we may here call it lost it's individuality. But there is no meaning of calling it losing individuality as individuality itself was illusion at the first time and creation itself took place by " he became many...".