Sion is my Ace in the hole, he can make or break your team honestly, His Strenghts are his amazing Ulti's and weak points are his early game squish-ness, quickly runs out of mana, so get Clarity, and Exhaust to slow your victims. I generally build with Dorian's blade, health potion, and ward, CAUTION! !!! Sion can be easily ganked because of his lack of movement spd, as well he has NO GAP CLOSERS, horrible v.s. Ranged, either you have ALOT of DEF and someone constantly ganking top or its GG. Sion sustain easily with a good start get 2 to 4 kills with out being taken down and you might as well control that lane.

After the Dorian's blade i work my way through the Ravenous Hyrda, Statikik Shiv, somekind of mag Resist or armor depending on foes. because by time they see you rolling around getting kills they will try to force you down. so get some sustain. Always be careful of where the enemy is on your map. Sion is not a ALL -IN -ONE. He gets shot down hard when he has 3 or more enemy pinning him. If you really wanna jerk them around a bit, get the Last wisper or Black cleaver for some extra armor tackling. after your set up your pretty good. just go with your normal ADC Melee items.