Dual Wield. The Shadowblade is just a magic using Rogue, be sure to stick with the default Backstabber trait and focus on getting behind the enemy and hitting them with backstab criticals, the damage is far superior to any other melee attacker and better than a lot of early magic users. By level 4ish you'll be destroying most enemies physical armor in one turn with a Rogue/Shadowblade.
Human or Elf is best for min maxing a R/SB, personally I'd take an Elf for the Finesse bonus and Corpse Eater.
Pump Finesse and Wits for attributes.
Adrenaline, Vault for the last one you can take Throwing Knife or Chloroform, either is fine.
Kill Kniles the Flenser in the Fort's dungeon as soon as you can as he drops double named daggers that will pretty much serve you until the end of act 1.
