Poisons are an extremely important aspect of the rogue gameplay. They will literally improve the class efficience as long as you keep them active on your enemies. As everything in WoW, you have to skill it up like a profession before to use it.
In this guide, We give you all the details of the rogue poison quests, for Alliance and Horde.

Why rogue needs poisons in WoW?

One of the unique features of the World of Warcraft Rogue is in the use of poisons. Rogues are the only WoW class that can apply them.
The poisons have a variety of effects, ranging from:

The poisons don’t apply with every strike, and they’re not devastating to the opponent, but they do have an effect and are pretty useful to have, especially in PvP.
So do the quests!
You can grab the poison quest at level 20.
Naturally, the Alliance quest is pretty easy and the Horde quest can’t be done by a 20 Rogue, not solo anyway unless you are that good.
Here are the details, Alliance first, Horde further down…

Alliance Rogue Poison Quest

Once you hit level 20 get yourself to the SI:7 building in Southwest Stormwind, climb to the top floor, and talk to Mathias, the leader of SI:7. He’ll give you the quest Mathias and the Defias. You might want to bring some anti-venom (Crafted from First Aid Profession at skill 80).

Step 1

Head to Sentinel Hill, in Westfall. Then, head Southeast to coord. 68,70.

Step 2

You’ll see a tower with some patrolling. A bit NorthWest of the tower is the person you want to talk to, Agent Kearnen. She’s hard to see, so look for the “?”

Step 3

She’ll give you the quest to get a key and then open a chest in the tower. Pickpocket the Malformed Defias Drone first and get the key from him.

Step 4

 Then open the chest, get the journal, get poisoned with The Touch of Zanzil.
Tips: – After you have the key stealth up the tower. Avoid or kill the patrols (lev 24) at your pleasure, – Klaven is at the top, guarding the chest. Kill or sap him, he’s only level 23 and is not an elite, – Use the anti-venom to get rid of the Touch of Zanzil.

Step 5

Go back to SI:7 and hand it in. You’ll get the Thistle Tea Recipe and you’ll learn the poisons skill. 6. If you need the cure for the poison then he’ll send you downstairs (get Touch of Zanzil quest) for the cure.

Horde Rogue Poison Quest

Horde has this one a bit tougher than the Alliance, but since the Horde ARE tougher… Any level 20 Alliance Rogue should be able to solo their quest, no sweat.
A level 20 Horde Rogue won’t be able to solo this one without help or some serious twinkage. So grab a pal or two. It’s not the level 22 guards that you have to think so much about, it’s the level 23 Elite you have to kill.

Also, you should bring an anti-venom with you.

Step 1

Speak with the troll Shenthul in Orgrimmar, in the Cleft of Shadow, at 43,53. He’ll have you do a salute. Just type /salute to complete it.

Step 2

Next you’ll do the Deep Cover quest and travel to the Venture Co. Tower, north of the Sludge Fen (Northern Barrens) and contact the Shattered Hand’s covert operative, Taskmaster Fizzule.

Be warned that Fizzule is extremely cautious.

Step 3.1

That Shenthul gave you a flare gun. You will have to use it to let Fizzulke know you’re coming. He’s at 55,05. Use the flare gun twice, as per your instructions, then approach Fizzule and use the salute, or else he’ll kill you as the Ally spy you obviously are. (use /salute) Guess he’s a little more careful, or a little more paranoid, than Alliance Agent Kearnen, who’ll talk to any Rogue at all.

Step 3.2

Fizzule will give you the quest: Mission: Possible But Not Probable.

Step 4.1

Pickpocket Foreman Silixiz at the base of the tower, to get his key. Do not kill him until you have the key. He won’t drop it, you have to pickpocket him to get the key. Then kill two of each type of wandering mob – patrollers, drones, and lookouts. 

Step 4.2

Get to the top of the tower and kill the 23 Elite Grand Foreman Gallywix who’s guarding the chest. Since you need his head, and he won’t just hand it to you willingly, sapping him just isn’t enough. 

Step 5

Open the chest (with the key,) get the goods, get poisoned, cure the poison with your anti-venom, head back to Shenthul to complete the quest and get the next one, Hinott’s Assistance.
Note: Unlike the Alliance quest you can pick this lock repeatedly (and you’ll have to kill Gallywix a few times as he respawns every few minutes) to work your lockpicking skill as high as 175 or so.

Step 6

Head to Tarren Mills in the Hillsbrad foothills, and deliver the Sample of Zanzil’s Mixture to Serge Hinott. Serge is the Alchemy Trainer in the first building on the left when you come into Tarren Mills. Serge will give you your poison skill and cure your Touch of Zanzil (if you haven’t cured it already.)

How to skill poisons up on my TBC Rogue ?

This is the easiest part of the poison profession.
Your only goal is to train new poisons and buy a list of ingredients from Poison Vendor.
Grab some golds and DO IT!
It’s simple as that.