@darkbard
All in all looks good. Looks like you guys had fun and did a very solid job!
Couple thoughts on the Discern Energies/Parley part:
* Its not clear by the excerpt (a) if the Tiefling's statement of "this one holds potential" is establishing/affirming that the Tiefling is capable of making that determination and has already done so (being in the line of work they are in) or (b) if this is just a best guess? Regardless, if the Duergar: Tiefling transaction already established the magical nature of the child, I'm wondering what you guys' thought line was on "Discern Energies revealing the child's nature" being leverage? Was the conversation something like "I can confirm your guess (if it was indeed just a guess)" or was it a bluff of "the child has x potential" (because the Psionic doesn't provide that info as I understand it?)?
* Given what I'm thinking I'm understanding in the reading above, I believe my order of operations would have been the following:
1) Was it not established whether the Tiefling knew for sure or not whether the child was magic? If so, leverage is good so the 10+ stands so long as the PC upholds their end of the bargain. Proceed to Discern Energies.
2) If it was established that the Tiefling did know for sure, then we need to sort out leverage a little more? Is the PC bringing something to the table like the aforementioned bluff "I can tell how potent this child's potential is?" That looks like good leverage to increase the price. If so, Discern Energies doesn't do the trick here and that looks to me like a Defy Danger Int (thinking fast and procedurally pulling off the ruse) or Cha (convincing and pantomiming the move and results of the divination). I'd accept either there.
On (1), if we got a hard failure on DE, then a lot of things can go down here; GM's choice. One option is "the Psionic discipline is lost until you re-attune (with no effect occurring)." In that case, she can't produce the goods for the leverage (because she can't "re-cast"). Does she come clean? If so, that seems like the time where you need to make a soft move to reframe the conflict. Does she try to bluff a consternated recast? Proceed to the second half of (2); DD Int or Cha. On a hard failure there, the rouse is up and there are consequences. On a 7-9, they buy the ruse but you change the situation sufficiently adversely so she has to make a hard choice (possibly something related to an alignment or bond), pay a cost (maybe 1 Coin for causing the delay in purchase and time is money to a slaver), or deal with a downstream complication of the ruse (maybe the Tiefling requests she come back to her steading and the PC show these exact magics to her Elders so they can study how the PC is able to determine how potent a magic is)?
Maybe you can clarify some of that and give your thoughts?