Ok, my creepiest herobrine encounter was when my friend installed a magic carpet mod last week.
he recently made this server, and I was alone on the server and found this sand pyramid. I went inside to investigate and I stepped on a pressure plate that was connected to a sticky piston, witch had an obsidian block on it. the piston shoots the obsidian block down and then he knocked all the torches down in the room. then this message showed up
Herobrine:well Tx2, it looks like we're alone.
Herobrine:there's no escape!
then this evil laugh came and BOOM he killed me in one hit.
and he lit my house on fire :/