My sources indicate that this was the first ever MMO circa 1997
I played this game for about a year in 2005 and had a 7x grand master swordsman.
I have never since played another MMO capable of providing me such thrills.
It was a lawless full loot game with real consequences. It provided you and others with many ways to be a true bastard. It also had player housing, and ships.
The housing system on the shard I played had a health system for player housing. If you didn't use the house, it would decay. Over time the house will collapse and drop all your loot and free up a plot of land for someone else to build a house.
The towns weren't exactly safe zones. People could pick your pockets, or just invade and kill the OP NPC guards. Pillage everyone.
One of my fondest memories involve a fisherman named Kindle. Kindle and I lured some stranger onto his fishing boat. We went out to sea, kindle locked the door and we murdered this dude on the boat.
In this game when you die, you do not respawn. You become a ghost. Your ghost has to visit a priest to be resurrected.
We couldn't open a portal to town because this dudes ghost would have been able to walk through it. Instead we just stood there fishing, while this dudes corpse and ghost were chilling on the boat. There was nothing he could do.
Eventually, we docked after we had enough laughs and his ghost was allowed to leave.
There were a lot of really cool things in Ultima Online. I never really got into the game but did play the next big thing that came along - Everquest. I nostalgia pretty hard about that game when playing a modern MMO. Theres definitely a lot larger sense of accomplishment when the task is slow and arduous. Most modern MMOs are super casual or easy which can be a double-edged sword.
I remember when you died in everquest you respawned naked at your bind point and had to get back to your corpse within an allotted time before it would disappear forever. Seriously, think about that for a moment. If you died it is likely your corpse is surrounded by monsters. In your now-naked state you have literally zero chance to get to that corpse without help from other players. That fostered a real sense of community that I don't really feel in the modern mmos I play. Another crazy thing I rememberd.. If you played on a pvp server in everquest and someone killed you, they could take a single droppable item off your corpse. It doesn't matter how rare and expensive it was they could just take it. Nothing like that exists anymore.
To be honest though... these days I don't have a whole lot of time for a MMO like I did back in my Everquest days. It is kinda nice to be able to hop on for a short period and get something done without having to grind 6 hours. That said, I'd not like to see the hardcore MMO market disappear like it has in recent years. I think a resurgence of things like EQClassic are an after effect of that.