Misty Escape is a class action usable only by Astarion if he completed his quest by ascending. It allows him to transform into a cloud which can fit thorough small openings, and has 
Advantage on Constitution, Dexterity and Strength 
Saving throws.
Description
Transform into a tiny mist cloud. It can't fall, and fits through small openings. It is very hard to damage.
The cloud has Advantage on Constitution, Dexterity and Strength Saving Throws.
Properties
- Cost:
-
Bonus action - Details:
-
Concentration
While transformed, you won't be able to attack, cast spells, or talk.
Condition: Gaseous Form
Duration: Until Long rest
- Transformed into a cloud of mist.
- Resistant to all damage.
- Has Advantage on Constitution, Dexterity, and Strength Saving throws.
- Becomes Tiny in size.
- Cannot attack, cast spells, or speak.
- The target's Strength and Dexterity scores are set to 10 while in this form.