With this build your main purpose is to protect your teammates and win teamfights.

This build has lots of CC some shields and good tankyness.

You can win bot early on with your good base stats your E poke and your Q that scares all champions from bushes. You don't do much damage but your adc can follow up and then get champions low hp and away from CS and EXP (their fear makes them run away).

Mid to late game you need to be in teamfights and beg for your team to fight (sion is really strong in teamfight by the way). You should be winnig but if top and mid loses you need to be carefull in teamfights. But if JG or BOT (or both) lose too try not to teamfight ever just make one of your teammate to split-push and other 4 of you protect tower. You shouldn't have any problems on defending towers with your AoE abilities and tankiness and CC.

Runes are made to support your team and most importantly the most fed person (who can ditch out the most damage). The runes that you can change are CONDITIONING and GUARDIAN for whatever you like. Because CONDITIONING doesn't help early game (but late game where all the teamfights come in it's really strong) and GUARDIAN because you don't have any abilities that affect your teammates or any dashes to close the diffrence to them (but it may help a bit in some situations thats why I take it). And you can take Revitalize instead of OVERGROWTH cause the making of the shields bigger may come in handy, but OVERGROWTH comes in handy for long games.

As I noticed that the item Face of the Mountain was removed when I was making this guide. Sadly it was the main core item, now it's replaced with Locket of the Iron Solari. This build is focused on shielding and winning lane and late game. The items are made defensive because as you know even lvl 1 Sion can hurt a lot with his Q charged, and his E poke AND if the ADC follows up. (The damage in late game is very low. But the CC makes up for it)

So you might wonder what's the order of skills in this build. I max Q first for its high damage easy knock-up and lowered CD and E second for biggers slows and lower CD for more constant armor shred. Then his W for % HP damage and the shield size.

As you could know the pro of this build is the CC, shields and the survivability in teamfights. The really only con can be that your team is ******ed and can't play the game well enougth to ditch out damage.

As in laning phase you should be very aggressive and get your enemies low with you poke and wait for them to close up to bushes just to destroy them with Q and when time comes you wait for you jungler or try to get oppertunities.

And late game you should focus the most fed person with your Q charged and E. But dont forget to use shelds on your teammates!