Essential Feature Characters or EFC's are characters that are very important to the MUSH. Without these characters, the Factions would have a hard time existing. There are the centerpoints of the theme, the leaders of the Factions, the people (or Aliens) that move things along.
EFC's are also considered the OOC 'Go-To Guys' for the ThemeStaff, to lead TinyPlots, or just every day Roleplay along. They may not be Leaders, but for the most part, they are are highly ranked in their factions, and as such, can control where people are sent, so can be able to help start many different Roleplay scenarios.
EFC's are not available for temping by Non-Staff members, and their applications are more in depth, as they require both the FC-Application and a Roleplay Test, and in most cases, a Trial period, during which, the character can be pulled, if the CharStaff and ThemeStaff believe that the player does not portray the character in the fashion that is best suitable for the MUSH.
On some MU*'s, EFC's are considered Staff, but on V:TVR, they are not. They are the bridge between Staff and players (But so are some RFC's and OFC's), they are Faction Leaders, all of them, by that, they are in the Faction System as a Leader, even if in the IC world, they are not a true leader yet. If a player has a problem, and is not ready to take it to a member of staff, they can go to a Faction Leader first.
Examples of EFC's:
For a List of all Feature Characters, See: Features.