(Spoilery)Tenzen was the Warrior of Light centuries ago

[TinyRedLeaf]

We are a "spitting image" of Tenzen which is the same thing the Alliance leaders say to us way earlier in lv15 story. That we remind them of the past WoLs they knew 5 years ago(talking about non-legacy here). I wonder, are all Warriors of Light simply reincarnations of a single person/a group of people.

It's definitely certain that Tenzen had the Echo. And the evidence does seem to heavily imply that he was also a Warrior of Light (ie, he likely possessed a crystal of light, just like Ysayle did).

But it's probably a stretch to say all WoLs are reincarnations of past heroes, because there's nothing to suggest that reincarnation exists in this reality. The closest we have to this belief system is that of the Dotharl in the Azim Steppe and, even there, it's heavily implied that " reincarnation" isn't what the tribe actually thinks it is.

As far as we know, when mortals die, their aether returns to the Lifestream, where it's "recycled" into new life and objects. That could be taken as a form of reincarnation, if you want, but it's not quite the same as old soul born anew, is it?

And as for the WoL the GC leaders mentioned, since you specifically stated "non-legacy", then no, those weren't Warriors of Light per se. It's simply how the survivors of the Calamity chose to honour those who fought in Carteneau that day.