When playing solo D&D, try making full on characters for the major NPCs. This can be more fun because (a) making characters is fun, especially higher level ones, and, (b) you get more faceted NPCs instead of just stock, one-dimensional characters.

I’ve been playing through Icewind Dale: Rime of the Frostmaiden and I applied this one of the duergar dwarves, Durth. In the published adventure, he’s a Duergar Mind Master. Instead of sticking wiht that, I decided to flesh him out a bit, making him a 5th level Artificer. This gave him a steel defender companion and access to interesting spells. I’ve never really played an artificer or looked at that class next, so it was fun to imagine that out. And, then, when it came to the encounter on the ferry in Easthaven, I had a lot more options than what a Mind Master would give.

This investment in time and imagining also creates a closer bond your NPCs. My theory here is that this will make their role in your adventure more interesting and genuin. You might get attached to them and want them to live. And, if you’re less likely to let them die and/or make dumb moves, they’ll be more interesting than just routine combat and encounters.

All of that takes extra time, of course, but one of the principles I follow in solo roleplaying is that it’s all part of playing. You take on the role of the DM, for example, which has all sorts of out of game work like this. And, you know: the point is to have fun! So if this seems like a drag at any given point, I just won’t do it.