Inktober is an annual art challenge that happens during the month of October.
Everyone is welcome to get involved. It's very informal. The creator of Inktober releases a lists of prompts, one prompt for each day in October. You use the prompts to create a drawing or sketch of that prompt, in any medium that could be described as ink (so traditional pen & ink, brushed ink or even digital ink). The prompts are optional and some people just draw what they feel like.
This was the first year that I managed to finish all 31 days of drawing. I was late by a few weeks though as I finished deep into November.