For many centuries it would seem the two Legendary pokemon known as Mew -the Deity of perfection, Light, and Love- and Mewtwo -A clone inhabited by the Deity essence of Darkness, hatred and Malice-

The conflict seemed never ending...

However Both Mew and Mewtwo shared a deep love for one another, while Mew kept her love out in the open, Mewtwo's love was more of a personal feeling something he kept to himself, or only in secret with Mew. The Two despised the fighting they were forced to do, and ultimatly wanted a path... a marker stone for ultimate true peace.

To this end Mewtwo and Mew mated while activly in their fully realized cosmos deity states. The Results were unprecidented... Mew had been impregnated by mewtwo who now was churning and developing the neutral essence of Twilight, a direction of purity of acceptance between light and dark. The lead for a perfect balance!

However Mewtwo, drivin by his desires to see a better world and have the perfect entity for his offspring be brought forth had used several machines to help Mew during her incubational period.... a mistake on his behalf.... as during that time foreign DNA was injected into the embryo.... the DNA of a Latios.

The embryo developed differently than anticipated.... it's body taking in the unnecssary Latios DNA.... Mew and Mewtwo Both feared the worst, what if the embryo didn't survive? Or was Faulty?

However as time progressed mew eventually gave birth to the mewbrid (mew Hybrid) and christianed him Mattmew....
Mattmew grew in a world that had already been altered by Cipher.... a place where many of the legendaries had already made themselves known.... and some had started civilizations
such as the lesser diluted mews who's purity of blood had fallen through the ages...

6 years passed and Mattmew found himself living in a crumbling city of Mews that reguardless of their losses were still thriving even in a world that was slowly dieing.... He ends up being visited by his Father
Mewtwo.
Mewtwo has waited 6 years for Mattmew to develop into a Deity.. only to see him remain a mediocre spinless mewbrid that seems to blame himself for everything that goes wrong around him.
In the eyes of Mewtwo Mattmew, their only true begotten son, an attempt at a perfect neutral deity, and a endless act of love... was a total lost cause and a Failure in every way...

Mattmew heard these thoughts and felt dispare.... his own father despised him... for being a failure in every sense of the word... from his powers to his appearance! However Mattmew's Deity Spirit Twilight Purity was going to do anything but Give up on the body he was developed in.... in an act of Cosmatic revelation and a bit of a push to get Mattmew's development under way... the Deity Essence infused itself to Mattmew's spirit causing his body to enter his "True" Legendary state.... in which he took on his true traits of both parents.... Mew and Mewtwo... as his body rejected the Latios DNA in him... causing his own Physical appearance to change.

With Mattmew's new found powers as a deity, alongside being a Mew, He has the power to filter and negitate darkness and light.... as per example a run in he has with his Father, who was over come with darkness... only for mattmew to start purifying him!
Mattmew must now learn the ways of a Deity.... and become the Legendary Pokemon he was born to be!
(most of this is taken from an RP I'm doing)