Surprisingly, this is slightly underpowered, though quite similar to the Lore Mastery subclass, which I will compare it to. Compared to the PHB classes only, however, it is balanced.
Borrowing Threads: This is far worse than Lore Mastery, which can change the damage types of any spell at will, and gets expertise in 4 skills, can use INT for initiative, and can change a saving throw, all at level 2.
Reweaving Techniques: You get access to counterspell at level 5, so it is balanced to give a once per long rest improved version of it. Similar to rogue spell thief, but more powerful as you are a full caster, not a third caster.
Correct Misthreadings: This is actually fairly weak, as you still use another spell slot, so all you are saving is an action. Compare this to the Lore Master, who by this time can prepare any spell they know as a bonus action, hit enemies a mile away, or increase their DC by 2. I would rather use my familiar or my allies to impose disadvantage on my enemies saves then spend another spellslot with another risk of failure.
Pieces of the Tapestry: This is on par with the Lore Mastery's ability. They get to cast any spell from any spell list once per long rest. You only get that for cantrips, but you can do it thrice per long rest, and can also get magic resistance or a free 6th level spell.
Recommended Language clarifications
- You should make it clear if spells cast by you/your allies count for
the Borrowing Threads feature.
- I would also make it so the Pieces of the Tapestry cantrip makes you
know that cantrip until the next long rest if that is not what is
already intended to do, as otherwise casting a cantrip once is
underwhelming compared to the other options. This would be on par
with the Artificers 10th level Right Cantrip for the Job feature.
Most of this looks fine, so I'll mainly focus on the outliers.
And boy-oh-boy is the level 18 ability an outlier. That said, I do want to preface this by saying that stepping outside the bounds of balance is the best part of homebrew. This criticism shouldn't distract from the fact that you've got a fun subclass on your hands; it just needs a bit of tweaking.
Umbral Incarnate is significantly more powerful than any other Sorcerer option, and probably any other ability in 5e.
I would be scared to put this ability on a BBEG, let alone a PC. As it stands, it will warp player choices across classes while simultaneously resulting in an unsatisfying gameplay pattern. Let's start from the top.
- Flying speed: by itself, this is a perfectly sound choice. Flight is prevalent at higher levels and lends itself well to over-the-top, dynamic battles. No problems here.
- 3x tentacle use + 2d6 force damage per tentacle: This provides far too much battlefield control and damage. This effectively allows the user to emulate a Repelling Blast/Grasp of Hadar Warlock's entire Eldritch Blast rotation on a bonus action. Martial classes salivate at the idea of this much battlefield influence.
- Thematically, necrotic damage would be a better fit for this ability.
- Recommendation: I can sense that this is intended to amplify the satisfaction of using the tentacles, which I think is a good goal, as it's the most unique thing this class has to offer. This should require a full action. As it stands, it provides far too much utility and versatility to be balanced.
- Magical darkness penetrable by you and your allies: very few creatures can see through magical darkness. To my knowledge, only devils and creatures with blindsight or truesight are capable of doing so. This means that the sorcerer and their party will be effectively under the effect of Greater Invisibility against almost every creature in 5e. All their attacks will have advantage, all attacks against them will be made at disadvantage, and they will be immune to any spells that require sight... at any range (as heavily obscured is distance-agnostic). With this effect alone, Umbra Incarnate obliterates this and any other similar ability in the game, bar none.
- Compare this to the Draconic Bloodline's capstone ability: it
inflicts the significantly weaker Frightened condition (disadvantage
on attacks + movement penalization), requires a save, requires
Concentration, is activated on an action, only affects targets
out to 60 feet, and provides no benefits to allies.
- This effect has anti-synergy with the flight ability, which encourages movement, as the Sorcerer will be encouraged to stay bound to their party at all times.
- Recommendation: this should just be regular magical darkness that only the Sorcerer can see through. Applying it to allies makes this stronger than just about any capstone ability in 5e. Additionally, this is too strong of an effect to be activated on a bonus action; make this an action instead.
- Frightened immunity: there's enough going on here already.
- Recommendation: remove this.
Overall, there's just way too much stuff in this ability, but it's not a bad idea. Tone it down and you have a cool kit-amplification ability.
6th Level has too much packed into it.
Either abilities are fine on their own, but I strongly prefer keeping Umbra Tentacle over Far Touch:
Umbra Tentacle is a neat, gameplay defining tool, as it:
- Requires no sorcery points to use.
- Takes a bonus action, meaning it's almost always available, as Sorcerers rarely take bonus actions.
I would clean up the verbiage to make it the source of the ability more clear (does it come from you or a point of your choosing?), but on its own I think this ability is a solid foundation to build upon.
Far Touch, however, takes this ability over the top. Umbra Tentacle is similar in power to each other 6th Level ability, so there's no need to cram another ability in, especially something as powerful as a cost-free Distant Spell usage on every touch spell.
Far Touch should be moved to 14th Level. Into the Void can go.
As the ability to see through magical darkness is an integral part of this subclass, in most cases the Sorcerer will want to engage enemies from the cover of magical darkness. As such, attacks against them will already be made at disadvantage, so Into the Void will rarely be useful.
Good news: this is the perfect spot for Far Touch.
1st Level is great!
1st Level is thematically satisfying and directs the Sorcerer into choices that will reinforce the thematic of this subclass. No tweaks needed here.
Best Answer
Not particularly balanced, no.
2nd level features:
6th level features:
10th level features:
14th level features:
The point is that if it's objectively better than all the other wizards, it's probably not balanced. That's not to say that you couldn't play it in a balanced way, say by making sub-optimal spell choices, but it would seem silly for most wizards to chose any other subclass. Also, if a dropout ends up doing better than most of the ones who stayed in school, what kind of message does that send to the children?