Oh yeah, taking evil!Brydolon to soto was the best idea.
Right from the start I got some amazing lore snippets for the both of them.
Brydolon's ability to see through the mists initially didn't sound any alarms. She could not interact with the visions she saw; there was no way to detect this ability.
When Brydolon learned to pass through the mists, pilfer items of interest, and channel the abilities of others she saw, the astral ward started to pay attention to her.
She was mostly harmless and only used her abilities to protect herself and Aimvara, so the astral ward chose not to take action and simply keep a strong watch on her for the time being.
Evil!Brydolon was another matter entirely. They didn't have the finesse that Brydolon had. When they tore through the mists, they left scars in the barrier.
But they were hard to catch. Hopping from world to world to plunder their supplies. They didn't contain themself to the Mist wars, and their actions directly impacted the survival of multiple worlds.
Now, I am still deciding whether the Astral Ward would have bit the bullet and enlisted their help, if they got possessed, or if they just continued on as usual. But I absolutely love all the ideas that soto has helped me come up with. I only made Brydolon's evil counterpart a few weeks before soto.