I agree, the game is awesome! so's the artwork you got here! =D

I love the use of colour

I think there is something odd with her pose. but maybe I'm just being confused by the dress' shoulder.

And yes, Muffet was one of my favorite bosses in the game.
Speaking of which, Undertale is definetly one of the best game I've played in forever. Everything is so weird but all the characters are lovable. The story itself might seem a bit confusing at first, but all is revealed in due time. A delightfull experience, I loved every second I spent playing it.
Plus, there are three endings. And each new playthrough feels completely new and different. You also get very different gameplay and experience for each ending you are trying to achieve.

You managed to capture the essence of Muffet with this illustration. I love it.

This is so well done!