Passive: Shadow of the Drow: Drizzt becomes stealthed every 7/6/5 seconds for 1 second.
Q: Blade Flurry: Drizzt dashes to a target, stunning it for 0.5s and dealing 60/100/140/180/220 (+Bonus AD) to it. 8/7/6/5/4s Cooldown. Passive: Drizzt Attack Damage and Attack Speed are improved by 10/15/20/25/30%.
W: Gift of the Drow: Drizzt senses the presence of nearby enemies, marking them but not revealing them in the fog of war for 2s. 20/17/14/11/8s cooldown. Passive: Drizzts magic resistance is improved by 15/25/35/45/55.
E: Fairy Fire: Drizzt casts Fairy Fire on an area, revealing targets within that area and lowering their armor and magic resistance by 10/15/20/25/30 (+0.2 AP) for 5s. 14/13/12/11/10s cooldown.
R: Guenhwyvar: Drizzt summons the legendary Shadow Panther Guenhwyvar to help him in a fight. Upon summoning Guenhwyvar will slow all enemies in a 400 radius for 2s by 35% and will attack nearby opponents. Guenhwyvars stats will equal Drizzts stats (+10/20/30% of Drizzts AP) and he will stay for 10s. 110/90/70s cooldown.
I realize there might be problems with copyright and such, so feel free to change the name of him and his pet. The theme of a Drow Ranger however feels appropriate for League of Legends.
Besides from that, I really like the idea of his passive, making him hard to focus and hunt down. Enabling some crazy jukes with good timing and really helping to build his drow ranger feeling. I adjusted the frequency of stealthing from my original post, as it was a tad too often.
His E and W have great synergy, helping at mapcontrol and in teamfights by giving strong support and once more focussing on the ranger lore.
His Q is a tribute to his uncontested two hand fighting style that often surprises the enemy.
Summoning the Shadow Panther is his signature move, as it greatly enhances his role as DPS/Support by an AOE Slow and significant damage output over the time of a team fight.
The Ranger excels at setting the stage for a teamfight, with the power to turn the tides of the battle.