I have looked and looked and there are not really any good AD Crit sion builds. With this build it will make it so much easier to farm and to wreck the other team. You will be as close as you can to being a god and unkillable even when people start getting Thornmail.

I would say Crit sion is like Gangplank except he has built in life steal and stun buttons to stay alive. Sion also believe it or not ends up with a lot more Attack damage than Gangplank and will crit for more damage.

Updated: 8/8/11
Moved Boots of speed earlier in item build.
Added Stun to the pros.

Pros:
High Damage.
High Lifesteal.
Have lots of health.
Has a constant stun.

Cons:
If you hit ult to late you can get shut down.
If they pile stuns on you things can end quickly.
Bad early game.
Ignite and other things that lower life steal can kill you.
Expensive build you must farm.

Marks: I go a mix of and Greater Mark of Desolation You can mix and match them to whatever works for you. Just make sure to have at least 9-10 armor penetration.

Seals: This you should go to help his early game. You could go Greater Seal of Vitality but I like armor better.

Glyph: This you should go to help your ability to be more of a tank late game. You could also put the if you didn't put it in the Marks but I would not recommend it.

Quintessence: This is one of the very situational runes. With this setup I go Greater Quintessence of Desolation. If you decided to not put in any attack speed in the marks then you should do so in the Quints and use . Mix and match these runes with the rest depending on what you own and what you like to use.

There is no set best setup for runes with this. As long as you get some attack speed and armor penetration then you should be good. The armor and magic resist really do help and allows you to be the beefy dps on the team.

Fairly self explanatory with standard Melee masteries. I go into the utility tree rather than the defense tree because you will not really need the extra armor and magic resist. The increased mana regen and more xp help you a lot more. The improved ghost is also a given.

Now this is what seperates AD sion from Crit sion. You may end up going some of the same items but the order and general idea behind the item choices are different.

We go to help add crit in the beginning and it will build into items later. Obviously pick up health potions.

Next you want to build . This is more of a means to an end and the extra gold will help your lacking early game.

Finally you get to finish out your . This is a very nice beginning item as it is fairly cheep and gives a lot of the stats that we need. Remember to use the active it can really help especially if you use it at the same time as your ult.

Now you buy your to get more magic resist and the tenacity. This will greatly help with running in and out of fights.

Next you want to build your . You want to buy zeal first because it really helps to have more attack speed. Then you want to get more crit so you buy the cloak . This is a really good item because it helps you chase attack faster and crit more often.

The main staple in this build is . Once you buy this you should see your damage output shoot up. Not only will your attack damage be really high but the added crit damage is amazing.

Next you want to get . This will mark your other big jump in Attack damage. You want to get the cloak first to just about max your critical chance. If you have been properly farming up to this point then you should have tons of health without even buying any hp items. The added armor also helps you out.

Finally if you get to this point then the other team just won't give up or no one is doing anything but farming. But if it does get to this point then buy a . This will both boost your HP to ******ed heights and bring your attack damage Through the roof.

Other than the first skill everything is very simple. You can choose to either go Cryptic gaze or Enrage. It does not really matter. If you are going straight for the level 1 gank then you should obviously get the stun but if you just want to lane then you should get enrage as it will help you last hit and get you gaining hp early.

: This is useful for chasing people and can help more than flash sometimes. I take this over flash because you have to get into melee range to be able to do anything rather than ap sion that can do stuff a farther distance.

: This is a all around good choice for Crit sion because it can shut down carries which is who you are aiming to kill. Exhaust can shut down a dps carry and will allow you to chase them down and kill them.

Other:
You can take instead of Ghost.

You can take instead of Exhaust.

Ok so Crit sion has a little bit of a different focus than AP sion. You should always be trying to help your laning partner get kills by stunning people. You should also try to save your team mate by stunning but if he is going to die don't follow him. You should be trying to get as many last hits as you possibly can. You should not lane with someone who is farm dependent like Nasus or Veigar. You can lane with a carry but you should try to stay away from the specific minions they are attacking and kill the other minions. This will result with an always pushed lane though so if you do this you must be very careful.

Once you get out of the hell that is early game you will start to pick up speed. Whenever you see a lane being pushed you should attempt to stop it and get some farm. Do not just leave your team sitting there in a 4v5 though. Make sure that your team can handle themselves before leaving to do anything. Like if the other team is pushing down one of your towers you should not leave to go farm in another lane.

End game you may get what I call God syndrome. This is where you do so much damage and have so much health you think you are god. However this is NOT the case. Always be aware of where the other team is. If everyone is MIA except one then you should not try to 1v1 them because their team will pile you. You also should NEVER go into a 5v1 unless several people in the group has low health and they don't have that many stuns. You can probably 1 hit the low health champions but make sure to turn your ult on before the fight begins because if you get stunnned or taunted you will need it to be already activated. If you activate it early and get taunted by someone who has thornmail you will not instakill yourself.

One of the things you have to be careful about is thornmail. Just like how it is the bane of gangplank it is the bane of crit sion. You almost always have to have your ult active to face these people otherwise your massive damage will kill you very very quickly. Hitting my ult early has saved me many times against rammus' with thornmail.

Don't bash it until you try it. Please leave constructive criticism in the comments and vote!