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This is the spec I have on my lock. It's highly effective and paired with my shadow damage gear, allows me to do sickening DPS and level incredibly fast. You can View My Suggested Spec Here.

The idea of this spec is to maximize shadow damage over time (DOT) attacks. With powerful enough DOTs, you can pack 2 or 3 damage attacks on an enemy, and they will die in time, no matter what you do. This allows you to pack on a couple DOTs, then pack some onto another enemy, and so forth. When fighting enemies my level, I will put my voidwalker on one enemy, put on a couple DOTs, then attack and kill another enemy. Then I go back to the first and deal a couple finishing blows and kill twice as fast as most players. You can also do insane damage by dropping a few DOTs and then powering an enemy to death with your other attacks or wands. There are also a lot of other tricks and advantages you can get. I'll go over each briefly.

5 Improved Corruption: This is REALLY helpful. Each time you improve it, it gets to a faster cast time. The key is, when its 5/5, it becomes instant cast. This lets you instantly put affliction and curse of agony on an enemy. In less than 2 seconds you have enough DOTs to kill most enemies. No matter your spec, I highly recommend putting these 5 points here first. It will give you a HUGE edge in battles. 

2 Improved Drain Soul: The mana bonus is nice but the real reason you want this is the reduced threat. This gives you a chance to keep enemies on the tank and not killing you.  

2 Improved Drain Life: This is hugely important for my mana/health balance technique for use later. For now, it will still help you a lot by allowing you to heal yourself more effectively. Remember, the more DOTs you have on an enemy, the faster you will kill them and the more you will heal with your drain life. On my lock, I can actually tank by healing faster than an enemy can hurt me using this skill.

2 Improved Life Tap: This is hugely helpful later on. When done right, you can finish a battle with full mana and hp. My lock hasn't had to take a drink in about 10 levels. I'll explain more in a later guide. For now just use this to tap your health for mana and a healer or food can recover you, or you can drain an enemy's hp to get healed.

1 Amplify Curse: It's got a cooldown but it greatly boosts damage or helps you greatly slow an enemy down when you're in a pinch.

2 Improved Curse of Agony: Huge bonus to one of your biggest damage sources. Make sure to get this.

5 Fel Concentration: You don't have to fill this up just yet, but it makes you able to drain HP while an enemy is beating on you. If you spec right, you can heal faster than an enemy can hurt you as long as this talent keeps him from interrupting your drain.

3 Empowered Corruption: Huge bonus on your second biggest damage source. The damage bonus goes up like crazy when you get more shadow damage gear.

2 Grim Reach: This is a beautiful skill. Increasing your range by 20% allows you to attack people who are out of range for them. You can kill them without them being able to even touch you in PVP. Also quite useful in instances when you need to stay WAY back. Also the further away an enemy is, the more time you have to kill them before they get to you.

2 Nightfall: This skill is really useful. It gives each hit from certain attacks a chance to give you an instant cast shadow bolt. Mine hits for about 1000 damage, so you can instantly cut off a huge chunk of enemy hp in an instant. It's only a 4% chance, but you hit the enemy so many times I get this effect about once every 1-3 enemies. Thats really often.

1 Curse of Exhaustion: This is REALLY useful in everything. When someone chases you, pop this little thing on and they can't catch you. It's perfect for DOTing someone, then running away. Most enemies won't ever get a chance to touch you if you're quick to slow them with this. I HIGHLY recommend getting it.

1 Siphon Life: Another crucial and awesome skill. It slowly drains enemy HP to heal you, no matter what you're doing. It also counts as another DOT which increases your health drained with siphon life. If I'm low on HP, I will drop this on an enemy along with curse of exhaustion and just run. As I go, my hp will recover. Sometimes I will put this on 5 or 6 enemies at once and recover hundreds of HP every second.

5 Shadow Mastery: Make sure you get this. It will basically increase all your damage by 10%, which is HUGE in WoW.

1 Dark Pact: This is another key to unlimited mana. It lets you basically use your pet as a mana battery. You just turn off their skills that use mana and keep their mana full. When you get low on yours, just hit this over and over to steal all theirs and fill yours up. It's like having an instant mana potion always on standby. I like to use my succubus because it does good physical damage without having to use any mana.

5 Contagion: Another 5% boost on some of your more powerful skills. Don't miss this one either.

2 Improved Howl of Terror: Another must have. Putting both points into this makes this skill instant cast. It is amazing in battle and can easily save your life. You can instantly hit this and all enemies around you will run away in fear. This will give you enough time to get away, kill them, or pack on another regular fear.

1 Unstable Affliction: Make sure to get this. It's a quick cast DOT that does a whole lot of damage. To make it even better, if someone dispels it, it will hurt them really badly and silence them. It's basically a death sentence.

This is all the talents I highly recommend. The rest of the remaining talents can be spent in any tree. I'll post more on my recommendation to spread out the last of the talents. I'll also post another guide as to how to use these skills you will pick up with these talents.

With these talents spent, you still have a few more to spread around. This is my recommendation on how to do it. The first goal is to get Shadowburn. This skill does instant damage in huge amounts at the cost of a shard. This is perfect for blasting your enemies instantly down in PVP so they can't have a chance to recover. We will need 11 points in Destruction talents to pull this off. Here's my recommendations:

5 Cateclysm: This isn't a must, but you will be using a lot of shadow bolts when your nightfall hits, and this will let them use up less of your overall mana. It's really up in the air here. You can also go 5 into Improved Shadow bolt. You will probably very rarely get this effect, but when it goes off, it will help you a lot. You could also split 5 points up between the 2 for a smaller chance for either effect.

5 Aftermath: This will make 1 in 10 of your shadow bolts stun your enemy for 5 seconds. This is easily enough time to kill them, so if you get lucky, you will instant blast their HP down, and have 5 seconds to kill them while they are helpless.

1 Shadowburn: This is the whole point of all of this. It will give you a massive instant damage attack to burn up your enemies with. It will use up a soul shard to use this technique, but if the enemy dies within 5 seconds you will get it right back. It's a perfect finishing move. At its final rank it will do up to 665 base damage. When you factor in all your other skills and boosted spell damage, this will be enough to cut off a huge chunk of enemy health instantly.

Other Skills: Now that you have all the important stuff, there's still a few more talent points to dabble with. I have a couple more suggestions, but if there's another skill you would really like, this is the time to get it.

2 Improved Health Stone: This makes all the health stones you pass out 20% more effective. This doesn't seem like too much, but when your health is low, the couple hundred HP can really make a difference.

5 Demonic Embrace: This will boost your stamina a lot. Lock gear usually gives a lot of stamina, so it will give you more HP bonuses the more HP you have. Remember every bit of HP can be instantly burned into mana.

1 extra point. Have fun, put it anywhere. I would go with improved voidwalker because it gives you a better shield when you sacrafice it, and allows it to hold off enemies better.  

I love the spec build you have but i think supersion is something that warlocks might like to put points into so they are less likely to resist you spells

Actually I put some points into suppression while I was leveling. It allowed me to fight higher level enemies effectively. When I got to level 60 and there were no higher level enemies to speak of, I respecced and dropped the suppressoin. I may actually put points back into them later. It's so easy when you're going for a certain skill, but it's hard to figure out how to space out your remaining points once you get there.

Suppression is a talent you definitely want to spec into if you are beginning to raid, or even while leveling. Reasoning being is there is very little hit gear available before level 70. That extra chance to hit allows faster kills, less resists and in raids, an easier time dpsing bosses. The time is not very significant but it is there at least