Lottie is an open-source animation file format. Lottie files are vector animations, that you can imbed on your website via a third party website or a plugin, or you can save them as an SVG file or do it the old way and save it as a GIF, some websites like give you some solid options for no cost.

The Ghost protecting the dungeon entrance is a Lottie file, keep in mind that the animation design should match your website design, and how you can use it to add something extra to your website.