Wow, this is a very intriguing poem!

I love the four different realms of life you touched on.

In this instance, I think the repetion is amazing and very well executed.

The first two stanzas are done flawlessly - great work!!

I have a couple suggestions for the last two stanzas just to polish them up a little.

The first 2 lines of these stanzas are fine, but the last two don't match up with each other.

Since you introduced the 3rd and 4th stanzas with subjects that are plural, (Spirits and Humans) you need to carry that through the other lines, so line three of those stanzas would be better as: Are we all dead? (This also matches the syllable count of line three in stanzas 1 and 2.

In line 4 of stanzas 3 & 4, basically you just need to change "is" to "are". I would also shorten the very last line to closer match the end lines of the other stanzas.

some suggestions:
Or are there other humans somewhere?
Or are there different humans somewhere?
Or are different humans hidden somewhere?

I hope these suggsetions help. You have a great poem here!