>>5257973Actually, we can simplify this even more:
<span class="mu-s">Charisma (Persuasion) Check: Convince Strahd to explain the full story involving Ireena/Tatyana.</span>
Roll 1d20+Charisma+Persuasion (1d20+0+2) to roll a Charisma (Persuasion) check.
(DC 18. Best out of 3.)
It's up to Aranuel to decide whether she even cares about this plot-essential information at this moment in the story; if this check fails, the information will not immediately be available, but can still be uncovered later by other means.