Oraculo EMU, was the first server I played, Chilean server from back in the day, 97d. Rates were like 3x. Zen was the main way of trading, and everything was really hard to get. I remember playing for more than a year and being only level 190. Lasted for more than 7 years, finally died when they moved to a "newer" version with easier content.
I always make hard servers, and I'm currently working on a complete redesign of MU, we are changing everything, so that the experience is similar to how it was when you played for the first time.. having to learn everything about the game again.
All formulas are different, classes are different, there are no stats (no str/agi/vit/ene/cmd), skills are auto-learned, lots of new quests, lots of new events, redesigned all existing events including castle siege. Redesign all sets/weapons (not visually though, not a fan of skins), sets can get multicolor glows, max level is 120, obviously no reset, ingame market system, new skills, new skill combos, new buffs, lots of new lore, new stats, a lot of customization for builds, complete redesign of parties and guilds with a lot of new guild-based content, new dungeons/raids and more..
We just loved the first time we played and we really want to feel like that again, having that experience of discovery again on this game.
It's been almost a year and a half of work, and it will still take at least another 6 months, but hopefully we'll have a really fun server.