Those who receive the mark of the beast will be thrown into the Lake of Fire alive — in the presence of Jesus and the Holy Angels.  Because they are not immortal, they die and are burned up in the Lake of Fire.  Thus, they never leave and the smoke of their torment goes up forever.  — The second death.

The Fallen Angels, however, are immortal and their torment is forever in the Lake of Fire.  They never leave the Lake of Fire.

Those who die unsaved without receiving/taking the mark of the Beast, are thrown into the Lake of Fire — dead never to live again — the second death.