To accentuate the hand-pencilled aesthetic of Mundaun, some 2D visual effects are animated frame-by-frame. In this case, it is a painting by Giovanni, the sinister artist of Mundaun. The things he paints seem to become reality.
The process: An initial pencil drawing is scanned. Parts of the drawing are then erased and redrawn for the next frame, which is then also scanned. This is repeated for all the frames. This process has the advantage that only part of the image has to be redrawn and the smudged quality of the resulting sequence also perfectly fits how a painter would move paint around on a canvas.
The images are then alternated in quick succession in the Unity engine, resulting in the painting coming to life.