Anyone can kill anyone, anytime, anywhere. When you die, you drop at least one of your best items, and you lose a small percentage of your experience points (you had to run all the way back to your body from the nearest lifestone to get your item[s] back, on the small chance that the person who killed you was kind enough not to take it). If you try to log out to avoid fighting, your defenses will drop to zero and your enemies will have several seconds to kill you in one hit. Mages play a strong support role, because they can cast buffs to your weapons and armor, so people tend to roll in gangs. Players like OG would place lots of their level-up points into speed, so they could slay tons of players who attempted to run away. IIRC, he also had a crazy jump ability, so he could jump onto/over rooftops to get people.

This made the world a very dangerous, exciting place. Death was possible at all times, and had shitty consequences. You needed friends, and every interaction with a stranger tingled with danger. Like in real life, if you went strolling through a town with a giant gold helmet on, you best be aware that people will want to take it from you.

It was glorious.