I can't remember well if I was playing Heroic or Legendary, but was certainly Story Mode (Thistletop Delve); with the right spells/items, I could find Nualia in the Warrens. I already had Lem there, but thought maybe it wasn't enough, so in Kyra's turn, I moved her there, encountered Nualia (what triggered that annoying monster summon) and proceeded to close the locations. Nualia deals 1d4 force damage to each character at that location, but oddly she dealt damage only on Kyra. I thought "ok, definitely a glitch, but for the better", and fought this first phase with Kyra, without caring about save resources since Lem was there to fight the second phase. After I won this phase, Nualia dealt her force damage against Lem. He lost some cards, but I could manage to win. Then I was surprised by the fact that the scenario didn't over and I had to fight again against Nualia, but only with a practically naked Kyra. Luckily, I won (if I remember well, my check was exactly Nualia's difficulty).

So Barl Breakbones has handed his baton to Nualia. Lovely!

I had a similar weird interaction with Nualia where she didn't do her initial force damage to everyone until after the first combat check.

 

http://forums.obsidian.net/topic/89940-legendary-thistletop-delve-progression-break/