One meal is enough to make them somewhat better disposed towards you, it is turning someone into a Creature of Darkness that makes more time.
Maggot Mana Plague (••)
With a casual gesture, the Infernal conjures forth fat, wriggling maggots from the Hell of Burrowing Maggots, grown fat on the souls of sinners. They writhe forth from the dust and then expire. Those who eat these highly-nutritious grubs find them delicious and nourishing, but also find their destiny bound to that of the Infernal.
System: The Infernal can only use this Charm in a place of desolation (defined as a place where Survival rolls are at least difficulty 8, or where most of the inhabitants feel despair at the state of their lives). She spends a moment concentrating and then spends 3 Essence to conjure her grotesque repast. One use of this Charm summons enough maggots to feed (Essence x100) people, and the maggots remain edible without preservation for a week. One meal of maggots is sufficient to feed and water a person for a day in even the harshest environment, but it also makes them vaguely loyal toward their Infernal benefactor; all of the Infernal's social actions against the maggot-fed reduce their difficulty by one. Those who exist on a primarily maggot diet become creatures of darkness after (Stamina rating) weeks, and may display subtle changes such as growing pale or soft-skinned over time; or may manifest features befitting the Infernal's personal Hell, if she has one. The Infernal's social actions against such beings reduce their difficulty by three.