The Mara are the forces of entropy and rejection of the cycle of reincarnation. Demons, monsters and others are all known as “Mara” and represent a terrible threat to the Precepts (of The Arcana). It is the responsibility of all people to be wary and watch for the influence of these demons, be they marauding beasts or unjust behavior manifesting the void.
Warlocks can make pacts with individual Mara, or other stranger things that lurk in the edges of the world. These are dangerous magics, and forbidden by the Courts (though it is said that The Court of Swords has been known to employ Warlocks to fight the Mara from time to time, as a sort of “fight fire with fire” solution).