The Last of Us will feature a clan-based survival mode in its multiplayer component, according to a set of leaked multiplayer details discovered in the recently released demo.
According to the leak, the game will feature groups of NPCs that can be trained and must be kept alive against waves of infected over the course of 12 in-game weeks. NPC clan members can be gained by fending off these waves and will grow as in-game weeks go on, however NPCs can die of starvation, infection, and other things.
NPC clan members can be sent on missions to improve their skills or to rescue other survivors and how well a player performs during in each attack wave will affect the overall health of their clan. Players will be offered status updates on their clan as the game progresses.
The leak also includes information on multiplayer weapons, crafting, and customization. You can read the full list here.