I apologize if this has already been posted, though I haven't seen it yet. The GMT Conversion Kit ad has Widow Tarha's hero sheet and a Magic skill/feat card on it. Setting the picture in Original size on BGG.com and zooming in the text is farily clear, except that some it is behind the box.
Widow Tarha's ability looks like it allows a reroll of some/all dice once per turn.
Her heroic feat looks like it allows 2 additional monsters within line of sight to be attacked. Based on what is visible, it looks like you roll one set of the attack dice but each monster defends separately.
The Dark Might card allows you to add a surge to an attack roll.