The Fear Lords are a group of seven demonic masters in the Marvel comics who conspired to rule the Earth and the entire universe through fear. They were opposed and stopped by not only by Doctor Strange and Daredevil, but by also one of their own named Stray Man (who betrayed them).
About the Fear Lords
The Fear Lords, or Lords of Fear, were first gathered together in to the Halls of Fear Dimension, a universe completely separate from the prime reality, by the Dweller in Darkness. The Dweller's goal which is the same as that of his felloew Fear Lords, was to make fear take over Earth and eventually the entire cosmos.
In Doctor Strange III #31, The Fear Lords meet within the Fear Dimension and introduce themselves to each other, describing where they each came from. The Dweller in Darkness informs the others of his plan to spread fear throughout the universe, starting with planet Earth, calling his vision the "Great Fear". All the Fear Lords supported Dweller in Darkness's plot - all aside from Straw Man, who wished to leave humanity out of it and left the meeting.
In Doctor Strange III #39, Straw Man manifests in front of Doctor Strange and tells him of the plans made by the other Fear Lords to douse the Earth in fear. Suddenly Straw Man, Strange, and Clea are ambushed by the Fear Lord Lurking Unknown, but their combined efforts defeat him. Not long after, the Fear Lords Kkallakku and Nox try to spread fear over Earth but are defeated by Strange, Clea, and Rintrah.
In Doctor Strange III #40, the Dweller in Darkness and Nightmare are tricked by D'Spayre into battling each other to prove superiority, with D'Spayre deciding to join whoever comes out victorious. Nightmare begins to poison everyone's sleep with haunting nightmares and Dweller in Darkness causes humans to be afraid during waking hours. Unfortunately for the two Fear Lords, the prolonged terror causes humanity's fear to turn into despair, and as the fear dissipates, D'Spayre grows more powerful. Dweller and Nightmare flee from D'Spayre, who is far superior to either of them, but D'Spayre is forced to retreat by the combined efforts of Doctor Strange, Daredevil (holding the essence of Straw Man), Clea, and Rintrah.
Within Journey into Mystery, all the Fear Lords except for Nightmare hold a meeting regarding the Serpent's assaults on Earth - Nightmare had decided to stay behind and take the fear made by the Serpent. Loki and Leah reveal Nightmare's ambitions of harnessing all the fear into a crown and becoming "King of Fear" to the other Fear Lords, resulting in the Fear Lords all fighting over it within Nightmare's dimension.