Among the other discussion about the Key Ability Score, it seems that people who do not like Charisma as the Key Ability Score tend to point to Intelligence as the alternative, but I believe there is a potentially stronger case for Wisdom over both Intelligence and Charisma.
To preface, this is operating under the assumption that the Investigator will receive a similar occult-themed subclass/class archetype in Dark Archives, and thus the niche of "Occult Investigator" is thoroughly filled.
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First, let's look at the flavor text of the class as presented within the class itself. Not any promotional materials, not any preconceptions one might have about the class, but what is explicitly in the written material contained within the class.
Keywords that show up in the flavor text:
- Exploit
- Connections
- Assess
- Manipulate
- Understand
- Investigate
- Research
- Look
- See
Many of these keywords refer to tasks typically associated with INT and WIS, but all of these focus on the same category of tasks: Discovery. This shares a parallel with another class, namely, the Investigator. However, while the Investigator focuses on material connections and drawing on the physical, the Thaumaturge draws on the spiritual and metaphysical, which is a strong representation of the dichotomy between the more rigid Intelligence and the more ethereal Wisdom.
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Second, let's look at the actual mechanics of Charisma in the class. What actually uses Charisma? Currently, it's Find Flaws (notably not Esoteric Antithesis), Binding Oath's bonuses, Counteracting with Chalice/Lantern/Sever Magic, and Save DC for Wand/Scrolls/Warding Circle. There's not a lot, and the latter two are necessitated by the current Key Ability Score, and would work with any other Key Ability Score. Binding Oath is the only ability that naturally uses Charisma, but Find Flaws is still worth looking at.
Now what is Find Flaws, exactly?
Quote:
You determine a creature’s weaknesses, whether a literal weakness or a metaphysical one. Recall Knowledge about a creature, using your Charisma modifier instead of the usual ability modifier for the skill you’re using to Recall Knowledge. The creature must be either one you can see or one you’re specifically Investigating in advance during exploration. The result depends on your Recall Knowledge check, which has the following additional effects as well as the usual effects of Recall Knowledge.
Note that the effect which actually uses Charisma is about learning and finding the weakness that you then use your training to exploit. Then, it specifically mentions Recall Knowledge, a typically Wisdom/Intelligence-based action.
Compare this again to the Investigator, which examines a creature to determine the best, physical location to strike from. Instead of using existing knowledge to formulate an ideal plan, the Thaumaturge observes the creature and perceives the hidden connections to divine a weakness where there might not be a traditional one. Another example of the material vs spiritual dichotomy provided by Intelligence vs Wisdom.
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Third, what does Wisdom do for the class right now? It's involved in every ability that uses Recall Knowledge Skills (Lantern Bonuses, Esoteric Lore, Rituals, Know-It-All, etc.) as well as a few Perception-based abilities (Lantern Bonuses again and Haunt Cunning). Compared to the one, singular ability that naturally uses Charisma (instead of an ability score replacement), Wisdom is far ahead. Even Intelligence falls behind, simply due to lacking in Perception.
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Fourth, why is it worth changing? Since flavor reasons are rather subjective, let's focus on the mechanical advantages.
1) The Thaumaturge simply has more abilities that interact with Wisdom. Between Perception and Recall Knowledge abilities, it simply does more for the class naturally than Charisma does. This allows it to be better at more abilities that it tries to support.
2) It provides a clear, concise fix for Find Flaws. Wisdom has the perfect replacement for Recall Knowledge when it comes to Find Flaws. Right now, Find Flaws runs into issues where it requires you to pump four different skills (five if you count Society for humanoids) just to keep up to par, struggles against creatures of higher rarity (which should be the Thaumaturge's specialty), interacts poorly with Recall Knowledge Skill Feats, and runs into a nasty clause where you can't actually try Find Flaws against a creature you've critically failed it against by RAW due to the way Recall Knowledge is written.
The fix for this is for Find Flaws to use Perception. That way, it actually *Finds* the Flaws. This allows it to scale from the class itself, gives it an edge against higher rarity creatures relative to Recall Knowledge users, gets around awkward Skill Feat interactions, and doesn't fall into the other issues with Recall Knowledge.
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Fifth and finally, what does it do relative to other classes?
This is the primary reason why I can see Charisma for the class at all. After all, it's already rather similar to the Ranger, and changing to Wisdom would make them even more similar. However, there are other avenues for differentiation, such as changing Esoteric Antithesis from a damage booster to a strong utility feature, such as a debuff mechanism.
Now, this can create even more interesting synergies. If players want a more "Monster Slayer" character like the current damage focus, multiclass Ranger/Thaumaturge would do that incredibly well.
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Overall, I believe this is a convincing argument as to why Wisdom makes perfect sense as the Key Ability Score for the Thaumaturge.
