I think that there should be some sort of way for certain types of Clerics to access the Thieve's Cant language.
There are a number of possible ways to approach this (examples below):
- Seeker Path: granted with 21 Seeker levels if Rogue levels are also present
- Trickery Domain: granted on level 21
- Cleric Deity set to Mask
- Some combination of the above
The specific rationale for this has both mechanical and RP justifications.
In terms of mechanics - as it currently stands, to my knowledge, a Seeker Cleric of Mask cannot enter the Thieves' Guild/Hideaway area, even with rogue levels, if they do not have the 7 rogue levels required to speak Thieve's Cant. This seems like an obvious oversight, especially given that there is literally a temple to Mask in that area.
In terms of RP, clerics of Mask in particular are treated essentially as "Rogues who pray a lot." The lore states that congregations of Mask are functionally not much different than a traditional Thieves Guild.
Accordingly, it seems like it should be the case that there is some avenue for Clerics of the appropriate path/alignment/domain/multiclass, to be able to "speak" the Thieve's Cant language, as they would presumably be able to communicate with their congregants / co-conspirators.
This seems like it would be relatively easy to implement, mechanically. And I think that the number of clerics affected by this would be few enough so as to maintain the "secrecy" of the Thieve's Cant, while also making a meaningful impact for the clerics that choose to pursue this sort of roleplay.
Thank you for your time and consideration!