I'd probably do it as a subclass.
OG Shadow Adept
I'd group the following abilities:
- Shadow Magic feats (Shadow Weave Magic, Insidious Magic, Pernicious Magic, Tenacious Magic): The OG is a bit of a grab bag making your illusions, necromancies, and enchantments better, and especially resistant to discovery and dispelling, and gives you a boost to beating the SR of other casters (which is also emphasized with the Spell Power feature).
- Darkvision (starts as Low Light Vision)
- Shadow Defense: Your saves vs. illusions, necromancies, enchantments, and darkness spells is better.
- Shield of Shadows: Your shield spell also gives you concealment and spell resistance
- Shadow Walk: Teleport to a shadow miles away or just into the Plane of Shadow
- Shadow Double: Create a kind of temporary simulacrum.
That, but As A Subclass
I think I'd favor a Wizard subclass, since we already have a shadow-themed sorcerer and the OG requires Arcana and Spellcraft (leaning toward an "academic" vibe). I opted to drop Shadow Walk, since the Sorcerer already has a feature like this (and the Shadow Monk does as well), so I opted to go for the more unique trait, the shadow double, for the capstone. The main highlight at most levels is that Magic Resistance doesn't apply against your spells, which I think is on brand for this archetype's story, and isn't gravely unbalanced (it won't come up in every encounter or even in every session). I expanded Shield of Shadows to also encompass Shadow Defense - since it's a level 10 free casting of
shield, this didn't seem too strong.
Level 3: Magic Pernicious, Tenacious, and Insidious
You have Darkvision with a range of 60 feet. In addition, spells you cast have the following benefits:
- Spells you cast cannot be perceived with Divination spells
- Any rolls made to dispel spells you cast are made at disadvantage
- Creatures with the Magic Resistance trait can't apply it against spells you cast
Level 3: Shadow Weave Magic
Choose a Wizard spell from the Illusion, Enchantment, or Necromancy school, or a spell that creates darkness, which must be no higher than level 2, and add it to your spellbook for free.
In addition, whenever you gain access to a new level of spell slots in this class, you can add to your spellbook for free one Wizard spell from the Illusion, Enchantment, or Necromancy school, or a spell that creates darkness. The chosen spell must be of a level for which you have spell slots.
Level 10: Shield of Shadows
When you are hit by an attack roll or targeted with an Illusion, Enchantment, or Necromancy spell, you can use your reaction to create a shield of shadows. Until the end of your next turn, you have a +5 bonus to AC, including against the triggering attack, and advantage on any saves you make against Illusion, Enchantment, or Necromancy spells. Once you do this, you can't do it again until you finish a Short or Long rest.
Level 14: Shadow Double
You can add the
project image spell to your spellbook. You can use this feature to cast it without expending a spell slot. When you do, the illusory copy you create is tangible and opaque, and objects do not pass through it. The illusory copy has hit points equal to half of your maximum hit points, and it cannot be healed. The illusory copy has the same proficiencies you do, and can use equipment just as you can. If a creature would notice that the illusory copy is an illusion, they see the copy for what it is: a blob of inky darkness shaped to resemble you, cold and damp to the touch.
That, but as a Feat
So, whittling down to only the truly essential traits, I'd preserve most of the low-level features. The higher-level effects can mostly be mimicked with existing magic, even if all the nuances aren't there, and a feat would allow a more diverse pool of characters to choose it (allowing again for druids, warlocks, paladins, etc. who use the Shadow Weave).
General Feat: Shadow Weave Magic
(Prerequisites: Level 4+, Spellcasting or Pact Magic feature)
Your spells can tap the Shadow Weave. You can increase your Intelligence, Wisdom, or Charisma by 1, to a maximum of 20. You also have Darkvision with a radius of 60 feet, and spells you cast gain the following benefits:
- Spells you cast cannot be perceived with Divination spells.
- Rolls made to dispel spells you cast are made with Disadvantage.
- Creatures with the Magic Resistance trait can't apply it against spells you cast.
Your spells do not gain these benefits if the creature casting the Divination spell, making the dispel roll, or possession Magic Resistance also possesses this feat.
Overall?
I think I'd be most happy with this as a feat in my own games - a little touch of something Other. The subclass is interesting, but most of the abilities are just riffs on existing spells, and those riffs could just be spells of their own that any spellcaster could learn (mmmmmaaaaybe requiring the feat to learn).
