Cold Blood

I've had this skill in my hotbar since I learned it and use it constantly but I honestly have no idea what benefit it's doing for me. All it says is "Your calm energy decreases your threat level by 99%." I use it like it increases my ability to not be noticed but when I use it near enemies they attack me, it gives me no info at all about what it actually does and I can't decide if it's worth keeping or if I should replace it in my hotbar with swift blade.

Anyone have more info I can use or advice maybe? owo