https://www.youtube.com/watch?v=6LEvpbkzYlU
This is RothUI. Uggly bubbles on health/mana bar are models. look, it actually shrinking as the character uses ressources / lose hps.
The background is transparent. There is no apparent illusion, or covering by black texture. Maybe something about multiplying pixels by a mask textures or a filter idk, maybe a scrollframe well used, but there is something very powerful i try to get.