I had a surprisingly tough time finding the deeper stuff for this pairing, which honestly shocked me given how popular both characters are in the 'Hazbin Hotel' fandom. Most of what pops up on the big sites is either pure smut or really surface-level rival-to-lovers fare that doesn't dig into the weird, manipulative, terrifyingly ambiguous dynamic they actually have. My breakthrough came when I stopped searching for 'Vox x Alastor' directly and started looking for fics tagged 'character study' or 'psychological horror' within the fandom, or even just browsing Alastor-centric works and seeing if Vox showed up as a complex antagonist rather than a love interest.
Archive of Our Own is definitely your main hub, but the tagging system is your best friend and your worst enemy here. You need to get specific: try filtering for tags like 'Emotional Hurt/Comfort', 'Psychological Trauma', 'Past Trauma', 'Complex Relationships', and 'Mutual Pining'—but also 'Emotional Manipulation' and 'Unhealthy Relationships', because let's be real, anything with genuine depth for these two is going to navigate that territory. I found a few gems by sorting by kudos but then switching to bookmarks and reading the comments; often readers who crave depth will leave more detailed notes. One story that gutted me was 'Static and Sinew', which framed their entire history through the lens of failed radio broadcasts and corrupted film reels—it used the medium itself to explore loneliness. It wasn't a happy read, but it felt true to them.
Don't sleep on smaller forums or even Tumblr threads, either. Some writers post shorter, more experimental character pieces there that never make it to the big archives. The search is kinda frustrating, but that one perfect fic that gets the poisonous affection just right makes it worthwhile. I'm still looking for more, honestly.