I accidentally stumbled upon this combination and found dramatic relaxation and deep sleep with no residual hangover in the morning.
From my understanding the black seed oil has some effect on the opioid system via its main active compound thymoquinone: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4387227/.
Pregnenolone seems to have some effect on the GABA-A receptors: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3356040/
I did not have this effect with either substance by itself. Previously I sometimes took diphenhydramine and hated the way I felt the next day.
I had been taking this combination in the morning and found I was really tired and unmotivated for a few hours. By switching it to night it has worked great. Sleep is deeper (as measured by my CPAP score - I have sleep apnea - as well as the sleep cycle app I use every night).
This combination feels really powerful - almost like a benzo. I'm 47 and also do TRT so that might have some impact. Anyway just an FYI for anyone who occasionally needs a little help with sleep to maximize your day.