Need some help figuring this out...
1) The description for the condition "Energy Drained" mentions nothing about losing 5 hit points for every negative level you sustain.
That's because you don't.
2) In the DMG, the special ability Energy Drain mentions losing 5 hit points for every negative level.
That's an error.
3) In the PH, the Enervation spell mentions nothing about losing 5 hit points for every negative level.
That's because you don't.
Which one is correct?
See previous answers.
When a target is struck by a Enervation or Energy Drain spell, do they lose 5 hit points for each negative level sustained?
No.
What about a target struck by a creature with the Energy Drain ability?
Also no.
Skip Williams
RPG R&D