Yes, Astarion is very clever but he couldn't read infernal. In my case Raphael had to tell him what was in the contract and I'm not sure if Raphael told him everything. Mephitopheles is his father even if he is angry about the crown of Karsus.

Anyway, I hope that there will be more possible for Astarion.

"Now, was that civilized? No, clearly not. Fun, but in no sense civilized" ~ Braingremlin