Here there be monsters was a phrase written on old maps to indicate unchartered waters. Ancient cartographers didn’t really know what was out there before the great explorers had sort of touched all the four corners of the globe. What was beyond the explored region was a question mark.

Lots of times on maps, unknown areas were depicted with sea monsters or dragons and it was often written, ‘Here there be monsters’ or ‘Here there be dragons’ (hic sunt dracones). The phrase is simply a variation on HIC SVNT LEONES ("here are lions"), the classical phrase used by medieval cartographers to denote unknown territories on maps. Because they didn’t know at the time what was out there, the assumption was there was something terrible waiting for them.