Hmmm.....how can I tie Columbus Day to Halloween?
I got it! Sea monsters!!!
Back in Columbus' time, his crew believed that giant sea monsters might attack their ships (of couse they also believed that the Earth was flat and they would sail off the edge of it).
The above image is titled Christophorus Columbus Ligur Terroribus Oceani superatis alterius pene Orbis regiones à se inventas Hispanis regibus addixit An. salutis. It is a print from the late 1500s.
Description: Christopher Columbus stands on board a ship surrounded by mythological sea nymphs and sea gods with Neptune or Poseidon being drawn by hippocampi (or seahorses) in the background. Decorative elements include sea monsters, whales, fish, anchors, banner with crucifix, a dove holding a cross, bow and arrows,and a banner with Columbus' coat of arms.
The original is in the John Carter Brown Library at Brown University.