A hard demon is a very hard difficulty term in a 2D square game called Geometry Dash.
You often need at least 5 rounds in practice mode to complete it, but it's often better to do runs from for example 50 - 100 so that you can beat it faster.
It feels like an extreme demon on 60Hz but if you're at higher frame rates it will feel like an insane 8*
I beat Forest Temple today on 60Hz, I know it's a Hard Demon but it felt like an EXTEME DEMON!
I have beaten 20 Hard Demons as of today, but it's way too less to call myself a legendary player.