In Curse of the Lady's Light, I think there may be some problems with Ashamintallu's tactics as described. The adventure states that she spends most of her time disguised as Sorshen via her change shape ability, and only reverts to her true form under certain conditions. However, the encounter description and her tactics state that she uses flight and her vampiric claws in combat.
This poses a problem. First, she should not even be able to appear as Sorshen with her change shape ability via alter self:
Unless otherwise noted, polymorph spells cannot be used to change into specific individuals. Although many of the fine details can be controlled, your appearance is always that of a generic member of that creature's type.
Leaving that aside, shapechanged into a human, she should lose both her flying speed along with her wings, as well as her supernatual vampiric claws ability along with her natural attacks:
While under the effects of a polymorph spell, you lose all extraordinary and supernatural abilities that depend on your original form (such as keen senses, scent, and darkvision), as well as any natural attacks and movement types possessed by your original form.
Finally, I think the stat block ignores the +2 size bonus to Strength she should get from using alter self.
How did other GMs handle this encounter?
I played it straight from the stat-block and the tactics provided.
It's a unique, it doesn't always have to be strictly like the rules usually work. My players understand that.
Ashamintallu had loads of time to work on her alter self, that it can be a bit different.
Hmmm. I've compared Ashamintallu's stat block with the referenced alu-demon entry from Frog God Games' Tome of Horrors Complete and noticed that the default alu-demon doesn't even have a change shape ability. Instead it has a 3/day spell-like ability to disguise self.
