I think the thottbot link does more harm than good here, since the information in the thread there is either outdated or inaccurate.
The encounter was changed significantly in 1.4, but some of the thottbot notes precede the change.
Also, "within an inch of their life" could be more specific. I'm pretty sure that possession ends once the possessed's life reaches 50%. (in 1.10)
--CheshireCat 07:39, 12 April 2006 (EDT)