Right now, we don't have anyone higher than Initiate in Nightsister.
There's a few ways we could tackle this. First, we do a thread in the past where you're both still part of your original lightside clans (darkside heavily growing of course) and you get trained by either Ti'Cira or myself.
Second, in light of the council of all clan mothers being formed, we make a story of you two running into one of us and working on a way for you to get training for us.
Third, and I just checked this and its allowed, I can NPC a Nightsister of higher ranking and get you guys training. Thinking this would be the most plausible option!
