Venat called the spell we know as resistance to tempering a "traveler's ward." Rather than a resistance to tempering specifically, it's a resistance to aetheric corruption in general, which is what we've learned tempering is - exposure to a concentrated source of an element that first hits the mind and eventually twists the body.
The Blessing may be what appears on the spinny board in what we now know is the Aetherial Sea after that first Echo experience. Hydalaen says it grows stronger each time the WoL overcomes a trial. We never got to get a glimpse at what the other Blessing of Light users saw on their spinny boards, but we do know that even the WoLs on the 1st collected their crystals in the same manner. (I think Ryne never hearing the voice of Hydalaen is because she had borrowed powers.... and by then Minfilia's will was barely separable from that of Hydalaen anyway. It'd be talking to herself.)
One more thing that I remember that is relevant to this discussion, possibly: when exposed to the Starfall, the people of the Crystarium described two distinct reactions: half of them felt a call to adventure, the other half felt a profound sorrow. All of them are sundered, but there's some speculation that those who felt sorrow were the souls of sundered ancients, and those who felt the call to adventure were the souls of those born after the sundering, who only knew the world post Hydalaen. Or maybe it is in reverse: those who were sundered felt the call to adventure, and those souls created after the sundering were more sorrowful because they were more susceptible to Meteion.
Both might be manifestations of the Echo or the Blessing.
