So because I'm fairly new still to the old ways, can you please explain, if the gods would come back as different beings/people? What about us?
Really big trees, like California Redwoods,
need wildfires to keep them alive. They kill off the smallest ones but leave the largest a little charred but fine. It's an equilibrium set up in such a way that it ensures the largest trees won't have to compete with saplings. It also helps destroy types of fungus that can cause the tree to rot.
I'm about to use
a lot of analogy here, so just ask if something seems amiss;
Yggdrasil is a giant tree. Or rather, depicted that way. Lots of branches, roots. We, and by "we" I mean "the universe as we know it" is upon the branches of this tree. Eventually, the dead & dying material starts to pile up. If it were allowed to do that indefinitely, the tree itself would die. But it doesn't. A wildfire rages, scorching the bark & burning the debris, leaving a bare but pristine tree free of ailments(well mostly, but I'll get to that). Eventually the smaller branches that were burnt away completely start growing back, the leaves and such do as well. But a tree never grows exactly the same way each time. In this way, there is change. In this iteration, we call it Yggdrasil, we call the Gods Aesir & Vanir. Our world is named Midgard. So on and so forth. But each time this happens, things are going to be a little different.
The plot is largely the same, but you've got some new actors & dialogue, basically.
Now, I mentioned that
most of the ailments of the tree are burnt away. What does that leave? Nidhogg. It lives, coiled around the roots of Yggdrasil, gnawing on them and on corpses. Sometimes it's described as a "dragon", but honestly that's under-selling it. I prefer to think of it as Entropy, the eternal, unending march towards oblivion. And It always survives Ragnarok.
There's also two other creatures, an eagle who hates it & a squirrel who ferries messages between the two as the eagle lives on the uppermost branches.