Jacob Isaacsz van Swanenburgh
After Paul Rumsey mentioned this artist I went hunting for more of his works. I found the above painting of hell in a book of Fantastic Art that I've had since childhood. So I've been familiar with this artist longer than I realized. The following 3 paintings were all that I was able to gather from the internet, apart from the other painting below that I'd mistaken for the work of Jan Brueghel. You'll be able to see the above work in far greater detail than the rest. If anyone can point me in the direction of more paintings by Swanenburgh, or larger examples of those posted below, I'd really appreciate it.
Hell, oil on copper.
Temptation of Saint Anthony, oil on wood.
Witches Sabbath In Roman Palace Ruins, 1608. Notice the large bird headed skeleton creature the witches are riding on at the bottom left corner of the painting.