Factions have the potential to allow you to gain reputation with different groups (hah, you know, factions, go figure) throughout the Mud. Based on your Faction Level NPCs and Quests might behave differently and open more content thank what you would have access to before. Use the 'FACTIONS' command to see where you stand within the different factions in-game. You can raise your faction level by either completing certain quests or killing certain NPCs.
Example of Faction display:
Faction Status
The City of Brass [Neutral]
The Hebdomad Council [Neutral]
Seraphim Angels [Neutral]
Cherubim Angels [Neutral]
Seven Heavens Archons [Neutral]