The Pen MC is a classic prison server that feels like the 2014 days. It is barebones and grindy and it does not try to turn you into an instant god. You mine you smelt your ore yourself and you actually have to travel through pvp zones to sell and stay alive.
You rank up from A to H and then you can reach Parole. After you hit the top you can prestige and keep going. The cool part is you are not stuck doing just one thing because there are different paths like mining fishing mob arena combat and a cookie bakery system.
Fishing is custom and can make solid money. The mob arena has waves and boss fights and you can earn money and shards with groups. The bakery path has you farm wheat and cocoa then bake cookies with custom mechanics and work on long term quests and leaderboards.
There are guards and contraband rules plus illegal crops that are high risk. You can rent cells and plots use the auction house place bounties do parkour and even end up in solitary. The server also says premium stuff is not pay to win because it can be earned through gameplay.

