Howdy Khalil Bodhi!
I like this part of Ajahn Mun's bio - source .pdf file here - warning long download time for slow connections
His confrontation with a malevolent spirit -
“I am a man of virtue. I have come here with the purest intentions – to practice Dhamma for my own spiritual benefit, and the benefit of others. Despite that, you threaten to pound me into the ground, giving no thought to the consequences of such an evil deed. Don’t you realize that it will drag you into hell where you will reap the terrible misery you have sown? Rather than feel concerned for myself, I feel very sorry for you – you’ve become so obsessed with your own authority that it’s now burning you alive. Can your potent powers withstand the effect of the grave act you are about to commit? You say you exercise sovereign authority over this mountain, but can your magic powers override Dhamma and the laws of kamma? If your powers really are superior to Dhamma, then go ahead – pound me to death! I’m not afraid to die. Even if I don’t die today, my death remains inevitable. For the world is a place where all who are born must die – even you, blinded as you are by your own self-importance. You are not above death, or the laws of kamma that govern all living beings.” The mysterious being stood listening, rigid as a statue, the deadly metal club resting on his shoulder as Ãcariya Mun admonished him by means of samãdhi meditation.
For me, next to the suttas - along with the commentaries, this is about as concrete as it gets.
I find the stories of the Forest Tradition masters fascinating.