Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This how i build up Sion..
For the skill sequence, you'll notice that i only put Level 1 cryptic gaze until i finished putting 5 levels on Enrage and Death Caress. That's because the stun duration of gaze is 2 secs no matter how high you level it up.
I level up my Enrage to 5 first because of the life that you can gain from it. Death Caress could give you another life/damage for early clashes.
For item build up. I usually go for warmog's first, Enrage+Warmog's bonus could give you a LOT of HP. That's pretty useful in the late game. I had a game which i made sion's life up to 5.8k with this build.
After warmog's, i go for capes because of the damage/sec and it helps you farm faster and could help you gain a lot of HP faster from warmog's and enrage. I suggest you to get the RED rune from the neutral monster for slow if you go on hunting.
Now after the cape, i'd go for the frozen mallet. this would really really help you a lot. aside from the HP that you'll get from it. the real purpose of getting that is the slow effect if you hit an enemy. no way he could run from you!
You don't really need much damage items early because you already have one from your enrage. It gives you 65 damage at level 5.
Now we go for the real damage! Atma's Impaler is the best Damage item for this build. I assure you that at level 18 if you farm really well.. you'd have at least 5.2k of HP. now do the math.. 5200 x .02 = 104.. that's a lot of damage. plus 45 armor and the 18% crit chance.
For the final item, I usually go for madred's. This could help you get rid of those tanks.. imagine adding up 4% of their life for your damage.. not just tanks, most of the mages stacks up HP at late game. some of them goes for 2.5-3k HP. That'll give you another 100-120 damage.. plus the aspd that you'll get from it.
For summoner abilities.. i don't think that i need to explain why i am taking ghost and cleanse.. you will own if you have this two.. cleanse for clearing out negative buffs + ghost for chasing/running off from enemies.
in addition, for the boots.. you may actually change your boots to ninja's tabi in the late game.. that'll give you +25 armor + dodge chance.. it's your call..
happy hunting sion fanatics!
BTW, for those who are afraid of heimer.. you'll own him even he's got his turrets with him..
goodluck and post your feedback once you tried this build!
the only thing that's lacking from this build is mana. so be sure that you always get the blue rune.. but it's alright anyways even if you don't.. lol