I summoned a warden from a spawn egg and played by making a fight with some mobs like iron golem or zombies. Suddenly then, in one moment, warden stopped moving and just acting like a dummy. This warden could feel mob sounds, but it didn't move, roar, or kill the mob.

You can watch a short video in this link, my channel.

https://youtu.be/hePbZ-kH7Kg