If we're ackshually things, lets cover the references to the lake of fire in the bible.

In revelations 19:20, there is the beast and the false prophet being tossed into the lake of fire.

In revelations 20:9, a bunch of people are explicitly consumed by fire from heaven. Consumed, not burned forever.

Then in revelations 20:10, the devil is added to the lake of fire with the beast and false prophet, and those three burn forever. But not the common folk.

Lastly, in revelations 20:13-15, hades and death give up their dead, and people are judged. Bad people are tossed into the lake of fire, explicitly labeled as a second death, but not mentioned as being eternal torment.

So in conclusion, the devil himself is spending eternity burning in the lake of "fire" (not lava or magma, nor is it underground, this is the apocalypse, this is happening on the surface of the planet that is being bombarded with heavenly shit), he's not doing any torturing there. He is also not the one sending people there, and sinners don't burn forever, they die when cast into the fire.