Nemo
After a long time, Lex eventually found out why the Cosmic sea was so dangerous to everything it touched. It was not that the sea would kill everyone, or destroy whatever it touched. Rather, it assimilated everything into it.
The Cosmic sea appeared to be liquid, but in reality it was its own type of entity altogether. It could not be quantified and solid, liquid, gas, plasma or anything else Lex was familiar with, because it was a diluted essence of what made up reality. Basically, besides chaos energy, the cosmic sea is what the Midnight realm was using to build itself up.
Only and only once all of the cosmic sea was used up would the Midnight realm finally exit the very initial stage of being formed.