if you were to say suck down a potion of storm giant strength or fire giant strength, then backstab firkraag would it kick his ass?

Dragons can't be backstabbed.

Heh, I tried...Kraggie just turned around and went after Yoshi

why not?

For the same reason you can't backstab slimes or beholders. It just doesn't let you. How are you supposed to backstab a forty foot dragon, anyway? Climb up its tail? Come on.

The books say that they cannot be sneaked up on.

Hhhmmm becuase you hafta be BEHIND the character your about to backstab (clever huh?) Unlike Baldurs Gate 1 (were you could do it untill they realased a patch to stop it.)

It is, as Armisael said, a question of practicalities!

You could try backstabbing the tip of its tail...

Alright i've got a fighter/assasin and he couldn't even backstab samia howcome
yes he was hidden
he has his thief skills
he was wearing shadow armor and sword of backstabbing
any ideas?