How can this description of heaven inspire an image of a peaceful afterlife with ghastly beasts & spirits?

Any out of boby experience is laced with bizare visions that don't usualy mean anything. The prophets and religious leaders of old just saw visions, not reality. The proper interpretation is forever lost and was most likely not even understood by the "dreamer". Yet they were so engrossed by the vividness they were compelled to write them down. Just like anyones dream diary today.