Players were given experience points to allocate into "Mastery Levels" rather than just their character level. You could invest in:

: Players who purchased goods in one city and attempted to transport them to another via horse or camel caravans for profit.

This system created organic, unscripted gameplay. There was no instanced battleground for this. It happened in the open world. A trader sweating bullets while crossing the perilous "Donwhang" bridge, hoping a high-level thief didn't appear, was an experience unique to Isro. The risk-reward ratio was intoxicating; losing a 5-star trade run meant losing massive amounts of gold and experience, but succeeding meant riches beyond belief.

Go to the official ISRO website. Do not use your main email password (security standard for any private server). Register with a username and password.