who and what is Apollyon ?

Answer 1

It is the devil, satan or whatever you want to call him. The Angel of the Lord will bind him for a thousand year in the bottomless pit. But he will be back, woe to us all.

Answer 2

"The destroyer". In the new testament of the Bible, Apollyon is called the angel of the bottomless pit. Abaddon, a poetic name for the land of the dead in the old testament, is Apollyon's Greek translation from the Hebrew language. Apollyon, in early Christian literature, is a name for the devil. He is identified as an angel of death, "hideous to behold, with scales like a fish, wings like a dragon, bear's feet, and a lion's mouth."