What are the use of spheres then exactly again? Do they determine whether you're allowed to spend xp on alterations? And that was unclear yes.
Let's say you want to create space fruit. You may create space fruit.
But maybe you want MAGIC space fruit. You can boost their Power by making them rare.
But let's say you don't want them to be rare and magical; you want them to be common and magical. So the way to do that would be to spend XP while creating them.
However, this is where Spheres come into play. Unless a creation is either an Unmantling or within one of your Spheres, you can't actually spend XP on it. So if you had the Sphere [Fruit], you could do so. If you were Unmantling to create them, you could do so. If the fruits boosted longevity and you had the Spheres [Fire][Pride][Sarcasm], you could not do so.
Do note that people rarely spend XP and I forget to check, so if somebody's been spending XP on things they shouldn't:
A. They've probably gotten away with it until now
B. You should totally rat them out to me so I can spawn a catgirl hit squad on their asses
Also, Pencil seemed to be wanting to invest the xp into the Verna directly, like for example how I invested into the Shards or Micelus invested into the Djinn, rather than investing it into some nebulous general technological advancement, with the the preface simply being a order to examine the technology of the Verna. Would such still be disallowed?
You may not spend XP retroactively. You may spend XP on a new action in an attempt to improve an old creation in some capacity, but you may not infuse XP directly into something that has already been produced.
Adittionaly, how would investment of xp into specific technologies work exactly? I'm a bit confused about the potential benefits it could grant, since the op rules mainly deal with how it effects creatures. Continuing that line of thought, how would are celestial bodies effected by the different power levels?
EDIT: And when unmantling to patron and forming a civilization, how would tweaking size and power levels effect the civilization exactly?
Depends on the specifics. To some extent, Power is open-ended; it usually gives magical abilities or exotic qualities, but the precise nature of these can be anything.
So in the case of technologies, that'd probably usually mean some magical or supernaturally skilled component. [Medium][Uncommon] Farming would probably mean simple rituals to farm better, or discovering exactly the right balance of plant and animal life to produce unnaturally efficient crops, or something similar. Along a similar line, [Small][Uncommon] Farming would probably mean similar, but steeply limited in some capacity; to certain times of the year, elevations, etc.
Positive Power levels for celestial bodies usually means they have some magical component to them; this can mean they're made of useful materials, they empower or enable certain types of magic, they radiate supernatural effects onto their neighbors, and so on. Lower power levels would typically mean they're nigh-useless in certain aspects- lack of materials, difficulty supporting life, etc.
Civilization attributes tend to focus more on organization and such than more solid creations. Size obviously tends to imply population and/or territory. Power can be a variety of things, particularly bearing in mind that civilizations as a whole can have attributes; for instance, the Verna civ is sadistically scholastic. Spending XP on that creation probably would have made them better scholars, but it could also have given them a stronger sense of nationalistic pride, better organization, or otherwise given them civ-centered gifts.
Would it be possible for Da'at to get a familiar too?
Yeah, with the familiar thing happening I was considering converting Sundancer into a giant biomecha.
Yours are the wings that will drink the heavens?
In any case, that depends on your definition of "familiar." You'll generally need to be of the right Tier to create or alter life, at which point making yourself a magic cat-thing that gives you magic cat-thing powers shouldn't be too difficult.