These devil-worshippers will receive no mercy from the "god" they serve so well. Satan will fry them in the hottest depths of hell as he laughs at their stupidity.
"Evil is the ultimate stupidity." These satanists personify both.
It won't be Satan frying them -- the eternal fire is prepared for Satan and his angels (Matthew 25:41, fulfillment Rev. 20:9-10). The unrepentant go there because sin has corrupted the entire human race, and thus God cannot stand sin or the sinner (Psalm 5:4-5).
That's why Christ had to become cursed, or hated, for us on the cross (Galatians 3:13). By trusting in Him, and His perfect provision, there is no condemnation, for He took it upon Himself (Matthew 26:39, Romans 8:1). The cup in Matthew 26:39 stands for the cup of God's wrath (an Old Testament concept).
God Himself will excercise His never-ending wrath toward the unrepentant as a demonstration of His perfect righteousness forever. Either Christ took the wrath on the cross for those who believe, or the unrepentant experiences that wrath for himself.
That, my friend, is what Hell is -- experiencing nothing but the wrath of God. No grace, no mercy, no love. That is certainly a far worse fate than anything Satan could do to us.