Tazorac is a retinoid, not a steroid. I pair HQ with Retin-A, also a retinoid. Both retinoids and steroids help HQ be more effective (and, in fact, there are products combining all 3 meds into a single tube), but I choose to avoid the steroids.

HQ works better on non-inflammatory hyperpigmentation, like melasma. It's not as good for inflammatory types, like the dark marks left after an acne lesion has healed. Personally, I think Vit C and time are about the only thing that help those.