(Crossposted from the reply on DTRPG) Hi Vlad, glad you enjoyed the book! You're right that it's only a bit akashic. It started as the Guru/Daevic archetypes and Zodiac stuff (plus an Eclipse archetype that didn't get printed due to some issues, maybe later~) and kinda snowballed from there.
Few things here. The Xeshim should still be able to shape veils that are listed in the Passion but not normally on the list. The Passion class feature reads "the daevic is granted the ability to shape additional veils drawn from a list associated with her passion." Meanwhile, the veil slots that are "passion veil only", which is what the Xeshim replaces, are from the Daevic Veilweaving class feature. But still, I will clarify to make sure the intention is clear.
With the Nebula, I wanted to make it focus wholly on combat, which is why it doesn't get the ability to summon champions. Plus champions are not a... super great mechanic? I was really hesitant to write a PoW "class" that got the ability to summon other PoW classes. Now, if you're a Solar or Lunar in a game where the DM also allows PoW, then Haab is gonna be your jam. As a houserule, I personally cap the number of champions a character can summon at the same time to 4. Starting with 1 at 1st, 2 at 6th, and 3 at 12th, and 4 at 18th (essentially following the E Cap from HD table). I definitely recommend doing this on your table, and get a feel for the limit you would prefer. I think your math is wrong on how many you can summon at low levels, though. A Morphbear Lunar at 2nd will have 5 E (assuming no other abilities), and the Extra Essence Human will have 6. Meaning they can only summon a single 5 essence champion (reduced to cost 4 by Lunar). And by the same token, since they have 9 E at 5th (10 for Human) they would be limited to 2 champions. Now if the Morphbear had Extra Essence and a bit of bonus E from an Akashic feat, they could definitely summon 3 at 5th. Which, again, is why I recommend limiting the amount that can be out at a time, and also level cap them.
There were originally going to be even more constellations to fill out the other Mayan/Aztec ones, a huge pile of Lost Constellations, but I was writing Haab near the end of the deadline and just had to get it out instead of taking another year on the dang thing. They'll probably show up in another book in the future, so keep an eye out.
I didn't consider the synergy effect of Dual Hemisphere. I'll have to look at that and see what I want to do about it... I might just leave it as is, you are still paying for both manifestations of the constellation, after all? I dunno.
Thanks again for the review! And watch out for my next book, which is gonna focus on the overlap of Psionics and Akasha, with a lot more akashic focus than this one ended up with. I'll just say "Veilknife" and leave it at that~