This enemy has a very large health pool, but low attack power and mediocre range with a short freeze effect. Not too bad by itself, but it is accompanied with pushers like Hearscht and it can be a rather annoying support.
Turn the animation on and off using the switch in the upper left. Clicking the viewer background enables scrolling and zooming with the mouse if on desktop. Note that browser zoom may cause issues with scrolling and zooming. A list of available backgrounds can be found here. For more info on usage, see here.