Challenging and deadly? I've done this myself - this is an assassin ( or nightblade as some call it) build, use daggers always ( except for fight dragons or something u can't sneak attack) and sneak everywhere, this way it will go up fast, use illusion spells like calm, fury and invisibility to deceive ur enemies and if u want to, become a vampire! ( 25% better sneaking and illusion) any questions about this play style feel free to ask
And the race for this is up to u, but for abilities, either an Orc or dark elf are great, dark elf because as a vampire u are less resistant to fire, but the dark elf starts with 50% more, and for the Orc, well let's just say u have a dagger with 10 damage on it, the assassins blade perk (15x damage with a dagger in sneak), shrouded gloves( backstabs do double damage) and u use berserk rage ( deal twice damage and receive half) then that's 10 x 15 x 2 x 2 = 600 damage on one hit without enchantments!!