What is the StarBlade?

Well, I don't have all of the details just yet, but let's talk about from different viewpoints.

1st the Design Viewpoint: It's my version of giving Draco a weapon that doesn't look to threatening or violent like a sword. Take Sora's original Keyblade, the Kingdom Key from Kingdom Hearts. It doesn't look threatening or violent looking yet that thing packs a punch. The Keyblade as well as the Master Sword from the Legend of Zelda series inspired this. As both can only be wielded by certain individuals. But unlike the Keyblade there's only one StarBlade, like with the Master Sword.

In game/Storywise: It's a magic sword like weapon, that originally belonged to a dragon named Scorchbreath, very long ago. Eventually Draco gained possession of this after his 13th birthday in his dreams. The Starblade has a lot of magic properties, but Draco hasn't been trained yet to learn how to use them, so all he can do in the 1st game is treat this like a sword, for now.