Use E to make the lane honest: it straightens the sidestep for Q, helps short-range R connect, and is often worth saving if death is likely because the slow can keep someone inside your passive instead of letting them walk away for free
Sion is strongest when his side wave and his crash path are both threatening, so shove top first and then disappear into a wall cut, river seam, or jungle turn for a short-angle ult rather than announcing a full-screen R from vision
Do not build your whole game around “inting Sion”: passive is for cashing a trade you already earned or salvaging a bad spot, and recent data shows the common early execute pattern is only modestly rewarding while high-death games still collapse hard
Group once your side wave has already asked its question or when your team needs your body to open the entrance to an objective. If dragon or Baron is the next real fight and your team cannot walk into the area without you, stop trying to squeeze one more side wave and arrive early enough to threaten brush Q, E catch, or a short-angle ult. If your wave is already shoved and someone has to answer it, you can hover in fog and keep both options alive. The bad pattern is staying in side until the fight has already started, then ulting through open vision from too far away.
After being killed, Sion will temporarily reanimate with rapidly decaying Health. His attacks become very rapid, heal him, and deal bonus damage based on his target's maximum Health.
Sion charges a powerful swing in an area in front of himself that will deal damage to enemies when released. If he charges for enough time, enemies hit by the swing will also be knocked up and stunned.
Sion shields himself and can reactivate after 3 seconds to deal Magic Damage to enemies nearby. When Sion kills enemies, he passively gains maximum Health.
Sion fires a short range shockwave that damages and slows and reduces the Armor of the first enemy hit. If the shockwave hits a minion or monster, it will be knocked back, damaging, slowing, and reducing the Armor of all enemies that it passes through.
Sion charges in a direction, ramping up speed over time. He can steer his charge slightly with the mouse cursor location. When he collides with an enemy he deals damage and knocks them up based on the distance he has charged.