Moloch is metaphor for the force present in situations where individuals, who each take the best options available to them, ultimately end up in a situation that nobody in the system would choose. When there is no individual whose unilateral decisions can improve the equilibrium, Scott Alexander proposed the name Moloch as the personification of the force that should be blamed for the bad outcome.
Moloch was used due to its treatment in Allan Ginsberg's famous poem Howl, of which the following is an extract.
What sphinx of cement and aluminum bashed open their skulls and ate up their brains and imagination?
Moloch! Solitude! Filth! Ugliness! Ashcans and unobtainable dollars! Children screaming under the stairways! Boys sobbing in armies! Old men weeping in the parks!
Moloch! Moloch! Nightmare of Moloch! Moloch the loveless! Mental Moloch! Moloch the heavy judger of men!
Moloch the incomprehensible prison! Moloch the crossbone soulless jailhouse and Congress of sorrows! Moloch whose buildings are judgment! Moloch the vast stone of war! Moloch the stunned governments!..
The topic of Moloch receives a formal treatment in the sequence Inadequate Equilibria, particularly in the chapter Moloch's Toolbox.