Sion/Strategy

Skill Usage
relies heavily on good skill timing and placement in order to be useful - his whole kit (excepting shield) is relatively unreliable to use. But when he can work well together with his team or just outplay the opponent, is a devastating force in team fights.
 * His passive,, will result in a revenge kill from time to time - but more often buys your team a moment with less pressure after your death, because opponents will be distracted by your continued presence.
 * Do not underestimate the damage he deals with . 10 hits will deal an additional 100% of the targets max HP and thus hurt squishy/slow opponents.
 * deals AOE damage and possibly knocks up targets hit. Fully charged and well placed, this ability can singlehandedly turn teamfights. While the potential threat of is huge, getting it to good or just any use can be quite tough.
 * To more reliably hit opponents, it is highly recommended to hinder the targets movement before charging . Hitting first with or even  will help for that a big deal. Also any further mobility reduction through teammates or items will let you charge longer for bigger effect.
 * Alternatively, can be a quite effective tool to zone opponents. For example, to block an enemies escape route or protecting an endangered ally by charging  on his position  does not need to hit.
 * A fast cancellation of will still deal one third of the maximum damage on the full range and slow the opponent briefly.
 * makes very tanky as the passive part increases his maximum HP over the course of a game. The active shield also scales with max. HP, which further increases this defensive potential.
 * Since it is unlikely that the shield will stay alive for two seconds in the middle of a teamfight, it is more useful to activate the shield short before the fight starts - in order to deal AOE percentage damage to the opposite team.
 * grants Sion a ranged AOE damage slow with armor shred.
 * Maxing first while pushing minions in lane grants  serious long ranged damage poke and wave clear.
 * Also, that damage is magical, helping against early enemy armor stacking.
 * Slowing opponents with will make it easier to engage on them or follow up with.
 * The armor shred lets your main target vulnerable to physical burst damage.
 * His ultimate allows him to move a long distance while also dealing high AOE damage and providing a knockup.
 * Canceling briefly before hitting the intended target will let you stop and deal damage at that position - even if the opponent gets away. This way  will hopefully be placed right where he belongs - in the middle of the fight.
 * A well used melee range is your most reliable tool to save teammates for example from s . It is pretty easy to hit and still deals half the damage and knock up.
 * Also passing distance with can be used to escape or to join a fight.

Item Usage
While pretty much any tank or fighter item is reasonable on, only the ones that synergize exceptionally well with him are listed here. So pretty much every item here is more or less defensive. That's why they are grouped by the additional benefits they grant to instead of their regular classification.

Mobility + Slow
Movement speed will improve 's potential to engage a fight without the ultimate and his in-fight positioning. Slows help him to land skillshots easier. Both effects make chasing and way more threatening.
 * are pretty decent, especially if you build Tenacity from a source other than.
 * grants his team speed and adds an AOE slow on top of that. Paired with health and some sustain, this item does a great job for . It can be cast during Unstoppable Onslaught, thus a well timed use of the active can let his whole team follow him into the fray. It should be noted that while it is a good item the stats it provides are useless as his w's passive gives him infinite hp scaling, late game he has more than enough mana, and his ultimate is one of the best initiates in the game. It's overkill.
 * grants the most movement speed possible from a single item. Furthermore it increases his early game offense a lot and also adds some defense. It's cost effective and is a good first item with AD, HP, and movement speed.  is all he needs for a powerful midgame. Just be aware that it provides little to no defensive stats.
 * is a good item as it provides mana and cooldown reduction, while also granting armor and a slow. It's a good item if you face an AD opponent in lane and the area slow will help your teamfights quite well. It is not as good as a Frozen Heart in most situations due to its extra cdr, armor, and the aura. Also Sion's ap scalings are low, so it is usualy not worth buying.
 * brings 700 HP and some AD paired with a strong single target slow - will be very annoying for your opponents. Combined with Furor boots you can take out almost any champion without large amounts of hard CC because they won't be able to kite you effectively, however the hp it gives isn't useful unless you're against true damage.

Offense
makes good use of AD because of his scaling with and  and the attack speed of. Also, building an offensive build will net you more focus from the enemy team. Sion also makes exceptional use of AP items because and  scale very well ability power.
 * is a pretty decent item because of the high AD, nice sustain and especially for the area damage. This way, can deal good damage to the enemy team, even if he has no other offensive items.
 * Another strong offensive pick is the . will make for a good defensive tool against mages early, granting resistances and a shield. Once upgraded into the,  will become more dangerous at lower health - and he has to die two times (or three with )
 * A is decent if you have to deal damage to tanks. With all the CC in his kit and four abilities that deal area damage, he can make good use of  passive. The HP and AP of the item will make 's shield also quite a bit stronger. Usualy building AP isn't effective on Sion due to his low AP scaling, however Liandry's passive can make up for this.
 * An early works well against armor stacking opponents in lane with  and.
 * A can be a good early item to control your lane and snowball more. It can then turn into a  that increases your early damage, gives you a movement and attack speed boost that can be useful to catch enemies with , gives you the option to reposition yourself to use your abilities and engage a teamfight or simply to have a better dueling potential.
 * Bloodthirster is potentially a very strong item on SIon due to the large AD and lifesteal. The shield is also very useful for defense. In most situations a Hyda will be a better item to help you cs better.
 * Blade of the Ruined King is a niche purchase, best used against mobile duelists that can dodge or interrupt Decimating Smash very easily. However the Blade of the Ruined King is only very good on auto attack dependant champions, which Sion isn't. If you find yourself dueling people often a Zephyr may be more efficient, as when combined with a  Youmuu's Ghostblade and a Frozen Heart you get 40% CDR which benefits Sion much more than the Blade of the Ruined King's passive and active does.
 * Rylai's Crystal Scepter is expecially good on him since it gives both AP and health to strenghten the shield from

Defense
gets tons of HP with the passive of, has a shield that scales with maximum health, and furthermore. While defensive stats are great for him, these items are more useful when paired with some other aspect, since tankiness alone will rarely win you a game. Generaly items that give pure armor and/or MR are much better for Sion than health items.
 * can be a powerful defensive item, supplementing your passive health gains and allowing Sion to return from the grave repeatedly.
 * Since they will pretty much ignore you after buying that item (because killing you will take forever), can work better on more offensive Fighter builds. In combination with for example a,  will be a threat that shouldn't be ignored.
 * carries a large amount of health and sustain that scales with max HP. Late game it will only be worth its passive.
 * is probably the best choice for armor, because the strong cooldown reduction will also support 's ability reliant usefulness. Furthermore, the attack speed slow works well just by staying in the middle of the enemy team. The lack of health on hurts  less than most other tanks. Also the 20% CDR it gives can increase Sion's damage output by a large amount, especially in lane.
 * The build path via is quite helpful early against an AD lane.
 * is a solid item for tanks and its spellshield might also help you to not be interrupted in your charge.
 * is a good item as it helps to last hit and increase your HP Stacking. This is also useful as you will be in the middle of the fight after inititating with.
 * Randuin's Omen, while a staple on nearly every tank or bruiser, benefits Sion even more. The active slow helps him land Decimating Smash and Roar of the Slayer, while the armor and attack speed reduction keep his Soul Furnace up longer and thus more likely to be detonated. Despite the large amount of health it gives its active can easily migitate the lack of usefulness of building health on Sion.