I'm honestly not sure that Sorin's choice of weapon is a particularly good one. Aside from being a unique item with an extremely high mana cost and called without any build-up or preparation, the creature it would summon is two or three times the power of your average dragon. On top of that, the very [i]nature[/i] of the weapon and the creature it summons would mean Sorin finding himself in a rather dangerous situation.
 
i.e., swordpoint.