Lucifer: An old threat

In the beginning, The Angel Lucifer was cast out of Heaven and condemned to rule Hell for all eternity. Until he decided to take a vacation.

The rest is history, Lucifer and Chloe met, they fell in love but were eventually separated by the departure of the Devil after understanding that he was too dangerous for Chloe.

An older brother of Lucifer decided to use the situation to his advantage by starting his plan to bring death to the first angel's and Linda's child.
And if Amenadiel can pay, it's killing two birds with one stone.