More SC speculation... some prospective builds that we could pursue with our XP. The build vote will probably take forever to come out if Birdsie has to write blurbs for every single level of every single relevant Aspect and Technique, so maybe this can serve as an interest check for pre-consolidation.
Some observations first:
1) Techniques tend to range from 100 to 250 XP at level 1 and most double in cost per level.
2) There are some exceptions like Wrath of Hermes that costs 2,000 XP and 25 SC, but we're not going to be able to afford that.
3) Techniques with base cost 250 are very strong and versatile - see Penelope's Retributor which gives +All physical stats and can also be used to generate additional XP itself in a feedback loop!
4) Less broad Techniques tend to start around 100 XP - see Comfy Magic and Connections.
Build Idea 1: Maximum Carnage
We have 27,500 + 1855 = 29,355 total XP
We have 4 free level 3 Techniques for Eldritch
Eldritch 8, Arcanum 6 (5,188 total XP remaining)
Buff Arcanum to 7.25 (0 Free Techniques remaning)
If Aspect : Level scaling holds, this gets us to level 18 in D&D terms - enough to access 9th level spells, though I expect in actual play each discrete Aspect level will yield its own 'tier' of superior spells, which is why 8.0 is so important. But that's not the focus here.
Buy Sanctum 1 and Technique: Connections 3 (4,850 XP remaining)
*Buy or Develop the Technique: Maximum Carnage, Level 3 - A Technique that reduces the Will costs of voluntarily entering combat, or of actions which might reasonably result in entering combat, by amplifying the symbiote's self-preservation instinct into a general 'battle instinct' that also grants it great intuitive skill at combat. Slight reduction at level 1, large reduction at level 3, eventually makes combat- and adjacent actions effectively free of Will cost. Maximum Carnage is a powerful Technique on par with Retributor, so Level 3 costs 250 + 500 + 1000 = 1750 XP. (3100 XP remaining)
*Buy or Develop the Technique: Lethal Protector, Level 3 - A Technique that basically grants all the shapeshifting-related effects of a Klyntar that the symbiote might previously have lacked, and enhances those already present. Form changing, bio-armor, rapid regen, clothing and disguises, mass generation, tentacle/weapon generation, etc. My understanding is that this does require a Technique to activate since baseline Eldritch only gives STATS and regen. Another broad Techinque like Retributor. (1350 XP remaining)
*Buy or Develop a Level 2 Arcanum + Eldritch Technique that makes Sol very good at buffing in any and all ways - haste, elemental resists, amped strength, entropic damage auras, etc. Improves the duration, breadth and effectiveness of all such buffs. Level 2 broad Technique, 750 XP. (600 XP remaining)
*Buy Hermes 2, more connections levels, or a slightly weaker Technique with the remaining XP. Sanctum + Comfy Magic, Coffee Jello Synthesis, etc. If more XP is needed, we can drop one of the above Techniques by a single level.
The idea here is to maximize immediate combat power and minimize the costs of entering combat by offloading much of the 'work' involved to the Symbiote. It hinges on us being able to at least partially influence the Symbiote's instincts and personality through a Technique, but this seems very plausible given what we've been told so far. With such power, we can rampage about and gather huge benefits. We mostly use Arcanum to buff and enhance ourselves and Penny, and in a pinch still have the utility of an 18th (?) level Wizard in our back pocket.
This will give us much more combat and exploration-related content and greatly improve our staying power as we merely have to cast a few large-duration buffs every battle, but I expect our top end here to be quite low compared to the other builds - assuming Eldritch 8 fights at the Arcanum 10-11 range and Maximum Carnage + Lethal Protector combined grant an additional +1 effective Aspect level for combat with another +2 effective Aspect levels from our incredibly powerful buffs, we can optimistically hit Arcanum 14 combat. However, most of this combat capability is constrained neither by mana nor Will costs, so in this specific field Sol can run rampant.
Long-term, we'd be looking at either Earth or Fire Devotions - Earth for the physical stacking if the Aspects stack like Arcanum and Hermes do, or Fire to maximize the power and utility of the few spells we do cast.
Build Idea 2: Simple and Good Part II
Eldritch 7, Arcanum 7 (7855 XP remaining)
Buff Arcanum to 8.0 (0 free Techniques remaining)
Buy Sanctum 1 and Technique: Connections 3 (7588 XP remaining)
Buy Coffee Jello Synthesis Level 3 - assumed to cost 1750 XP (5838 XP remaining)
Buy the best Will-generating or discounting Technique we can get, Level 3 - assumed to cost 1750 XP (4088 XP remaining)
Buy Hermes the Destroyer 4, 3500 XP (588 XP remaining)
Simple, straightforward and absurdly powerful. This build leans into Solomon's strength as the King of Magi to achieve Arcanum 8.0 casting (estimated 20th level D&D Wizard) and a whopping Arcanum 7 + Eldritch 1 + Hermes 8 = Effective Arcanum 16 rating in battle. Arcanuum 15 can destroy a city block with a single action and an entire city with effort; this build achieves the level above that.
The remaining XP is spent to defray our Will weakness by any means possible, but can be converted to flex XP to pick up any other Techniques we find particularly appealing. We can also buy a bunch of Level 2 Techniques instead of a few Level 3s, or drop Hermes to Level 3 to free up 2k more XP and dump it into Connections, etc.
This build doesn't rely on somewhat speculative Techniques, it simply exploits the existing Aspect stacking mechanics to great effect. Possessing unparalleled versatility both in and out of combat, we can easily use these capabilities to steer Solomon towards whatever content we want to see. An all-rounder build that, due to the sheer breadth of magic it can access and raw power it can wield, can conjure a serviceable solution to most any scenario. Its fundamentally high Arcanum level means all our subsidiary Techniques like Connections, Coffee Jello Synthesis etc will get a huge boost in actual effectiveness on top of their base Level.
Long-term, we'd be looking at either Air, Water or Fire Devotions. This build can excel with any as it is a generalist outperformer that fundamentally relies on casting magic to do things. With Air we'd focus on Hermes hoping to get versatility via conceptual destruction, as Air's domain encompasses all spells which are offensive in nature regardless of what objective they seek (proactive defense, excising an infection, deleting the concept of a wound, deleting the concept of resistance in your opponent's mind). Fire and Water are naturally highly versatile and wouldn't have this issue, but Water isn't quite as convenient to cast with.
Build Idea 3: Capitalism, Ho!
Eldritch 7, Arcanum 5.9 (16,605 XP remaining)
Buff Arcanum by 0.5 with half the Eldritch Techniques (2 free Techniques remaining)
Sanctum 6 (605 XP remaining)
Make our Symbiote our Sanctum and let it leave our body with the other free Techniques (0 free Techniques remaining, spend XP on the Sanctum component of the Technique if necessary to make it function)
*Buy or get Penny to buy a Technique or Aspect that lets her sanctify agreements, making violation of the spirit of the agreement impossible or at least really, really hard and with massive penalties. Should not be out of range for Justice.
*If XP is insufficient, drop fractional levels of Eldritch until we have enough. Going to Eldritch 6.9 would free up several hundred XP, for example.
With Sanctum 6 we can make our Sanctum in Pangothica and return to it (Discord info). Arcanum 6.4 is D&D level 16, more than sufficient for mass Teleportation. We sell access to Pangothica to the upperclassmen in exchange for bountiful favors and a cut of everything they extract, then let them strip mine it down to the bedrock. Sol profits massively without having to do any work himself. If attacked he can retreat to Pangothica which is nigh-unreachable without his aid. This level of Sanctum also lets us move our Sanctum without much issue so we can move it to Bible World right before they graduate in order to maintain our unassailability. The nominative and Architectural synergies there are obvious enough.
Within his Sanctum he's probably still quite a formidable mage, and even outside of it Arcanum 6.4 provides very decent combat capabilities. With the powers and favors accrued thereby, we can spend some of them to compensate the Gothic Horror class for stripping their world bare of any and all value - or just give them free potions that allow faster scaling than naive exploration anyway. Given this will grant Sol a significant percentage of the progression value of an entire world, it should scale pretty well but who knows, really?
The downsides, of course, are a massive lack of XP efficiency and pretty crappy performance (compared to the other builds) outside the Sanctum. In an emergency where we can't teleport out but can draw the Symbiote back to us, they are fighting Eldritch 7 + Arcanum 6.4 + Full Power Sanctum 6, since our Symbiote is our Sanctum. We could also use this to just stay in / further explore Pangothica, serving as transport & enhancer for Penny who solo clears all the encounters and gives us half the spoils.
Long-term, Fire Earth or Water would all be serviceable Devotions here. This build doesn't require as much Will regen since we won't be doing any work ourselves, just taxing the efforts of others... like a King.