First BIG Campaign

I'm doing my first large scale campaign. Full world building and everything done by me. But I'm having trouble thinking of how to start it. One idea I've had is starting off with the party dead in some way and make their first major quest regaining their bodies and figuring out what happened to them, who or what killed them. I'm just stuck trying to figure out a good way to do that, maybe even check out or make some homebrew subclasses that would work well whatever I can come up with for how they start.

Greetings LoordChungasss,

Welcome to the D&D Beyond Forums :)

Creating a full world, and building a full campaign (multiple long adventures strung together) can be very challenging and time consuming, but rewarding if everyone has a good time at your table.

As you did not state what books you own or have already read, or what experience you have with the game (playing or DM'ing), I'll start with some basic suggestions...

First off I'd read through the 2024 DMG, as it walks through being a DM and creating worlds in a much better manor than previous editions.

Additionally D&D released their Dungeons Master's Workbook of Worldbuilding back in the spring which might be helpful for you.

There are also tons of free resources online to help your worldbuilding like World Anvil and others.

Cheers!