The Big Theory
I'm sure that most people on this list will disagree with me, but I personally believe that Rebirth provides the most compelling evidence for answering the big question - 'what the hell is Lucas?' Clearly Lucas is not invincible and is not omnipotent, but he is pretty powerful (make sure you don't stop reading this sentence one word from the end!). Watching Rebirth, it occured to me that perhaps Lucas has no greater abilities than does Merlyn when she inhabits a human body. Maybe Lucas is nothing more than your normal run-of-the-mill dead guy. OK, so he's a very manipulative and evil guy, but maybe other than that he's the same as Merlyn in this Ep (and others.)
Think of Lucas's main NON-HUMAN 'talents' (excluding charm, manipulative abilities etc.)
1) The ability to control weather/nature.
And also consider Merlyn. Remember Merlyn when not with a human soul can only be seen by Caleb (and generally wears a white dress). When in 'human form' Merlyn can
1) Control weather (lightning in this Ep)
It is also interesting to note that Merlyn (when only in 'dead' mode) cannot be seen by most of the people. Only Caleb and Lucas know she's there. If Lucas is 'dead' could this be how he finds out certain bits of his 'inside information'? Being invisible could get him a LOT of useful flaws in people to pick at!
Oh, I've just thought of another. Why when Caleb dies in LTC are the only people who are in 'heaven' Lucas, Merlyn and he? He is in a state of almost dead/almost alive as is his sister, but Lucas......? Note neither of his parents (DEFINITELY dead) are there.
I'll be interested to see who disputes this first, and if ANYONE will actually agree with me!
p.s. The only flaw to this theory that I can think of is why Merlyn's body disappears on her dying in Rebirth, whereas Lucas's (presumably) does not when he is killed in TBSH. I could speculate as to 'one was murder, the other suicide' etc. But any suggestions?