I Prefer 9 Greater Mark of Desolation For more Damage.
9 Greater Seal of Alacrity for more attack speed,
9 Greater Glyph of Alacrity for even more attack speed
The quintensess i get are based on everything we need

Armor penetration:
Greater Quintessence of Desolation
Attack speed:
Greater Quintessence of Alacrity
And a little bit movement speed:
Greater Quintessence of Swiftness
Optional Runes



At low levels Stun costs a lot of mana, you can get some Greater Seal of Replenishment for mana regeneration

get 3 Greater Quintessence of Desolation for more damage
or 3 Greater Quintessence of Alacrity for attack speed

Skills and usage

Cryptic Gaze: (Active): Sion's gaze terrifies a single enemy, dealing magic damage and stunning for 1.5 seconds.
Cost: 100 mana

Cooldown: 12 / 11 / 10 / 9 / 8 seconds

Magic Damage: 70 / 125 / 180 / 240 / 300 (+1.0 per ability power)
Death's Caress: (Active): Sion surrounds himself with a shield which absorbs damage. If the shield is not destroyed in 10 seconds, it will explode, dealing magic damage to surrounding enemies.

Cast again after 4 seconds to manually detonate.

Cost: 70 / 80 / 90 / 100 / 110 mana

Shield Strength/Magic Damage: 100 / 150 / 200 / 250 / 300 (+1.0 per ability power)
Enrage :(Toggle): While active Sion deals extra physical damage at the cost of health each attack. Additionally, he permanently increases his maximum health whenever he kills a unit. The health gain is only there if this skill is active.

Cost: 6 / 8 / 10 / 12 / 14 health per attack

Attack Damage Increase: 25 / 35 / 45 / 55 / 65

Health Gained: 1 / 1.5 / 2 / 2.5 / 3 per kill
Cannibalism :(Active): Grants Sion lifesteal and +50%/75%/100% attack speed and 50% attack speed for 20 seconds, additionally Sion's attacks heal surrounding allies for a percentage of the damage dealt.

Cost: 100 mana
Cooldown: 90 seconds

Life Steal: 50 / 75 / 100 %

Heal: 25 / 37.5 / 50 %