In secret to no one In creation Raphael and lilith were in love and in secret they would have sex hidden from adam,but during lucifer rebellion she joined him in hell.
At this time she gave birth in hell to half-angels one of them such as mazikeen
(The reason for this is in the show they didn't say who the father of demons are,yes,lucifer and adam are not the father of demons)
The hellish energy from hell gave birth to the first demons as they no longer had their angelic half anymore.
Raphael(deku) was even more sadden as he decided to go to a distant galaxy,unleashing his rage he destroyed a couple of planets and stars in rage and more so sadness.
He went on back to heaven not showing his true feelings to others.
Not even going to sephiroth or metatron or even Jophiel as he trained by himself alone not talking to his mother and father.