How do I write a prompt that keeps the same character across multiple Midjourney images?

I'm trying to create a consistent character for a comic-style series using Midjourney v6. Every time I generate a new scene the face changes slightly even when I use the same prompt.

I've tried adding "same character", "consistent face", "character sheet" but nothing fully works.

Has anyone found a reliable technique for this? Would love to see examples if you have them.