I’ve started running Curse of Strahd and have been having a ton of fun making wacky homebrew things for my party and tweaking the module. Unbeknownst to the players so far, I have made them all a secret Dark Power trying to use them to usurp Strahd and Vampyr, and they’re just waiting to offer their dark gift.
For example, I have a druid with some fire giant ancestry who loves Produce Flame and is their front line, so he’ll be offered a slightly weaker Rage with the Path of the Storm Herald desert feature to use once per long rest. The celestial warlock would get charges to boost his Eldritch Blast damage and some secondary healing in exchange for sapping his life.
Giving my players powerful upgrades alongside typical class advancement can make some encounters harder to balance around, but as long as we’re all having fun who cares about balance??
I also love the world building, but I think I approach it from a different direction. Rather than prepping sessions, I like to build mechanics and details into the world. These are often informed by the actions of my players, but in the game it allows me to run a similar “zero-prep” style because the world already exists. Especially after several campaigns in the same world, when so much has been generated over hours of play.
The experience of seeing my world unfold before me, and seeing the wonder and emotion on my player’s faces, brings me so much genuine joy. I feel like I did when I was a kid.