There are 7 different factions in Tibia, of which you can choose only three. They are:

• The Efreet and the Marid factions. Chosen as part of the Djinn Quest.
• The Nightmare Knights and the Brotherhood of Bones factions. Chosen during the Dreamer's Challenge Quest.
• The Secret Service Factions, which include CGB, AVIN and TBI. Chosen during the Secret Service Quest.