This is my first guide and I want to show everyone a way of playing Sion that keeps him alive for the whole game. This build has enough AP early game to harass and health regen to stay in lane for a long time.

Marks of insight are important because of how much Sion's abilities depends on AP

Seals of clarity are perfect for Sion, if you use him correctly you should not have any mana issues at the beginning of the game and these seals really help in mid game when you have enough health to last a long time.

Glyph of Force or Potency here but I choose force because with Sion's stun at level 1 the opponents will not get very close to you for fear of being stunned and dieing. Also, without a couple ranks on your shield it will be difficult to burst anyone down. this is why it is better to have the ability power later when your skills hit harder.

Quints of potency give you just enough starting ability power that your Q stuns and hits for decent damage that it is a great counter-gank or harasser. This also gives your shield enough damage to take the whole minion wave to below half hp at low levels.

The masteries are pretty standard for an AP based champion. You take the points in offense to get increased mana regen then the rest of the points into utility. The points in utility allow your stun and shield to have a lower cooldown and also give an increased movement speed so you can get in range of your opponent faster. Having a increased cooldown on flash allows you to flash in then stun then blow up your shield for some easy ganks.

Starting off with regrowth pendant and 1 HP pot allows you to stay in lane forever with Sion. I do not take doran's ring because I would have to take a lot of damage to try and get a kill at early levels and I would rather sit and gain exp and gold to go for kills mid game. Go back once you get enough gold for your sorc boots and that will allow with your shield to make it very hard to die on a gank. After the boots you head back into the lane and stay until you have enough for Warmogs or at least the high health belt that builds into it. After building Warmogs you should be much harder to kill and can soak up more exp and gold to start building into deathcap. Once you get Deathcap your runes should really start to kick in for some increased AP and mana regen that allows you to use your stun and shield several times before you have to leave combat. After this you can really build any number of items that allows you to counter your opponents. Lich Bane would be a standard choice because it would allow you to hit harder after your skills go off. It would also give some increased mana and movement speed, but I don't often get to buying this item because the game is already over.

The only type of skill order you need on Sion is to pre-charge up your shield so that after you stun the opponent you can catch up to them and pop the shield right away for lots of damage. Your E should stay on all the time to help increase your melee damage. Sion's ultimate is not very helpful for an AP build. The only times I use his ultimate is to burst down towers or if I have low health in a lane and need more. Also if there is a 5v5 fight going on then it is a good idea to pop it, this will give your team a little bit of health back while fighting.

The only two that I use are ignite and flash. Ignite helps a lot because after you stun then and pop your shield most champs will try to run and your skills will be on cooldown again. Ignite helps you to keep some damage on them and you can flash up and stun them again for the kill. I find that flash is great for both initiating to flash+stun+pop shield and also to get away from flashing over trees or under a turret. Ghost is not used because Sion's melee attacks don't hit very hard so chance are if you can keep up with your opponent you will not kill him unless you have some abilities off of cooldown.

Like I said at the beginning this is my first guide so any feedback would be greatly appreciated. I have found Sion to not be a very common champion but the way I set him up and play him the other team spends a lot of time trying to kill me which also means a lot of time my team has an advantage. With the stun and shield I can counter just about any gank even 3v1 early game. Also, If my allies can get to me I can turn around and stun the gankers for an easy kill. I am really having a lot of fun playing Sion and I hope this guy helps others do well with him. I will try to put the items/runes links in the test when I figure out how to do that!