Some NPCs can be readily identified by the tabard they wear.

Player Factions

Societies of Dereth

The War of Blood and Shadow Factions

Isparian Factions

Derethian Factions

Aluvian Factions

Gharu'ndim Factions

Sho Factions

Viamontian Factions

Empyrean Factions

Creature Factions