"or find a source of negative energy"
https://mkaku.org/home/articles/the-physics-of-time-travel/
"one version requires vast amounts of negative energy"
https://mkaku.org/home/articles/the-physics-of-interstellar-travel/
"Negative emotions are unpleasant and disruptive emotional reactions. Examples of negative emotions include sadness, fear, anger, or jealousy"
https://www.verywellmind.com/how-should-i-deal-with-negative-emotions-3144603
"Far in the past before Atlantis existed,
men there were who delved into darkness,
using dark magic, calling up beings
from the great deep below us.
Forth came they into this cycle.
Formless were they of another vibration,
existing unseen by the children of earth-men.
Only through blood could they have formed being.
Only through man could they live in the world."
https://www.crystalinks.com/emerald8bw.html