I'll try my best to reach the deadline but I'll say in advance it will be Kroot. Every Inquisitor needs tribal bird-man slave to deal with things and eat them, right?
Added a purely non-combat, non-intelligent, non-psykery and non-trained-to-steal-things pet to Astra's character sheet after conferring with @Maleth
Casvasy means 'Tau' as in Imperial Assignment rating, I think. See http://wh40k.lexicanum.com/wiki/The_Assignment #OneOfThoseObscureBitsOfFluff
Yes he does. It's a snake.... As a notable constant in a sea of change, Astra's favourite accessoire is a long, slim reptile similar to terran varanidae.
#Nitpick; Snakes aren't varanidae, but ironically some varanidae (like the 'Dragon itself) belong to the toxicofera clade alongside snakes.