The question was asked, “Is Hell reserved only for Satan?” The answer is in the negative. Hell is a place of pain and punishment for infinity that has been reserved not only for Satan and his demons, but also for all those of us who die in unrepented of and unabsolved mortal sin – that is why the latter is called “mortal.” You can learn more about mortal sin here and here, as well as about Hell here. You can also read about being in mortal sin and the great mercy, tenderness and love of God our Father.
In brief, when one has a mortal sin or sins on their soul, they may, to all intents and purposes, be alive in the flesh, but they are dead in the spirit. In other words, they are walking sepulchres. However, when one dies with even just a single mortal sin on the soul, they condemn themselves instantly to Hell, not Purgatory, because since the Holy Trinity is pure and immaculate, They cannot reside in and where the darkness of sin resides in full.