That's my most unusual artwork so far. I just randomly went with the idea of a gender swap for Gaster, and of course there are already a lot of artworks on that theme. So I didn't do my own interpretation; instead, I was inspired by this cool design by ChaosCat08: https://www.deviantart.com/chaoscat08/art/Female-W-D-Gaster-857620477
You are free to copy, distribute and transmit this work under the following conditions: