Even the most powerful pit fiends in Baator lived under a shadow of anxiety and fear. Although they possessed formidable power, that was compared to ordinary devils. They were direct subordinates of Archdevils instead, subject to more stringent requirements and treatment. Even the slightest thoughtlessness would engender punishment.
The harsh treatment and death threats from their superiors was a curse no devil could escape— unless of course it was someone at the peak of society, an Archdevil!
Consequently, when the seven Archdevils publicised their agreement to let their underlings battle for the Second Hell, many pit fiends went wild. The Dark Eight were only the first wave of entrants, and many more devils would end up participating. Even the dragons and gods of Avernus couldn’t resist the opportunity.