CyphirWrath

I had this exact problem shortly after I bought my S8. In my case, it turned out to be Avast antivirus that was causing the drain. More recently, I have found my phone gets hot in my pocket. It turns out that if I place my S8 in my pocket with the screen facing my thigh, it heats up. Perhaps something to do with the Always-on-Display feature. This has only occurred within the last 2 months or so, after a software update I believe.