Create entity by particles

Hello! Im trying to create an enemy by pure particles. I was thinking about creating a enemy made of darkness. But I cant find anything about creating an enemy by particle system. its very tricky and I dont seem to create the result I want. Maybe a shader I can use or something to simulate the enemy made of darkness. (I will need it to have animations but I can handle that.)

I already tried using mesh particles. *A good reference could be a good help! maybe images. Thanks in advance!