I want to create a homebrew DND or Pathfinder based campaign. I have some ideas, that I want to structure properly, some campaign-specific mechanics. I also want to flesh out my world a bit more, and design couple enemies and NPCs that fit my setting well. What information do you need from me for doing this task?
To help create your homebrew campaign, I'll need the following information about your campaign's world, setting, and characters. Here are a few questions to help get started:

1. What is the setting of your campaign? Describe the world and its inhabitants.
2. What is the main story or plot driving your campaign?
3. What are some unique mechanics or systems you would like to incorporate?
4. What kind of enemies will your players be taking on? What are those character's strengths, weaknesses? What are they driven by?
5. Do you have an existing backstory or lore that you want included?
6. Are there any specific mechanics or systems you would like integrated into this campaign?

Providing detailed information such as the above questions will significantly assist in my understanding of what you wish to have in your campaign and help me bring your ideas to life.
It's still a fantasy world, but it's got a post-apocalyptic vibe, a prison should be  location for the story.
I want the character to break in and out of the prison at different points. You can make up the reasons; friendship, vengeance, idc.
A major mechanic is the prison break. Especially as the PCs realize that they will need to do it repeatedly, if they're smart they'll start leaving tools and partially ready paths for themselves, without leaving signs so obvious they'll be detected while the group is away.
Enemies are the prison guards, who are somewhat generic. Also some of the prisoners become enemies with unique personalities and abilities. One might even be an ally at one point who becomes an enemy. There are also classic enemies throughout the campaign, since there is a world beyond the prison.
That's what I've got in mind, please fill in the rest for the start of this campaign.
Alright, the prison itself is called 'Dantalion Penitentiary'.

The prison is guarded by Morpheus Guards—they are a small unit of elite warriors, but they have a few weaknesses: 

• They are vulnerable to heat.
• Their armor has a small gap on the backside.
• They will freeze when splashed with water.

There are many guards and prisoners within the prison, but here are some important figures:

• The 'Warden' is a man by the name of 'Kronus'.
• The 'Head Guard' is called 'Atlas'.

Kronus is a middle-aged man with a deep scar across his right eye but a surprisingly warm appearance. He's a cunning and ruthless leader, and the reason why so many of the Morpheus Guards are still loyal to the prison. However, they still don't fully trust their boss.

Atlas, the head guard, is a tall man and has a mysterious past with Kronus. He takes after Kronus in almost every way, apart from his cold personality. While Kronus shows warmth, Atlas is known for being ruthless and is usually the one that executes unruly prisoners.

---

You find yourself in a small padded cell, wearing thin tattered clothing with a small metal bar. The room has no windows and is quite dank. You don't seem to remember how or why you got here, but you feel a surge of adrenaline, and your instincts tell you to escape.
Looking through the bar, you can see a metal door, two guards, and a few prisoners in cells near you.