My first theory and i don´t know if i will contribute another but that idea came to during the premiere and i didn´t see the idea around here, so...
Some inital thoughts about the spring in which the Others can heal
people and, as we know now, has even resurrection-capacities (which of course confuses even the Others).
First of – it is clear that the spring obviously has some healing-capacities, which of course come for a price.
I think the spring could be some kind of portal which makes it possible to draw (yes, dark tower) the conciousness of the one who is drowned (or should i say baptized?) in there out of another reality.
The hourglass basically is the amount of time which is needed to make the process work.
We know that this healing-process changes the one who is healed in an as of yet undisclosed way. This may be the key. Could it be that the "drawn" conciousness contributes some life-power to the wounded? Will the memories of now two conciousnesses be merged to one in which the actual memories of the wounded one take lead after a short time of confusion but that the other conciousness somehow changes the cahracter a little bit?
What i wanted to say is that the spring maybe the portal to all the other ATLs and maybe thats exactly what is Flockes destination...
Thank you and good night!