Nice build! but i agree with The Teddy Bear and get rid of Zhonya's hourglass for archangel's staff( my opinion always).

Nice item build but I think that I would go with a Archangels Staff instead of a Zhonya's Hourglass just for the extra AP and mana stability but thats kind of a personal opinion so keep at it!+1

hm, much better now, but id still change seals and glyphs in ap/lvl since those give a lot more. items are much better now too, zhonyas before rylais could be marked as my personal preference^^

masteries: perseverence is ****, take buff duration and flash mastery. its been calculated often enough^^

since w doesnt get a longer root and increases more in mana cost than e u should be getting the 2nd rank in w at lvl 8. not such a great differences but a small difference can actually make the difference :D

^^: i already did rework them, it might have not updated when u last saw it. and 2 ranks in nevermove i find best because if you lead it, it is very rarely avoided.

Well, then go ahead and rework this stuff pls. And maxing ur e after getting one rank in everything will give u more dmg since its very easy to land - good players will often dodge ur root so u gain much more from e.

@ ratteasd: yes, magic pen was meant to be in, but i was experimenting with cdr + i hadn't gotten to adding the Void Staff. The MP5 Runes can easily be replaced because of the masteries that give regen. And i do max my E, just not right away to keep sustained damage throughout those levels. But i do thank you for the help :D

lololol, sb voted this up :DDDD

Need Sorc Shoes, some MR item, more magic pen, basically ^

Mages, your weakness, burst damage, will just eat you up with 30 magic resist.

Not a great build at all. Why?
Items: First, u dont have enough mpen. sry but without sorc shoes and/or void staff everyone will simply get some mr and ur dmg wont do anything.
2nd is that u should get more ap after ur roa, the slow from rylais isnt that strong since u have a slow and snare and ull need ap to heal more. go for zhonyas or rabadons earlier. its also stupid to say that u dont get mana probs and put clarity as a possible option for swain. just no, u have an amazing passive which wont let u get oom ever if u dont spam.
Runes: Yellows should be mp5, or ap/lvl, but not flat ap. doesnt help u really much since swains ap ratios aint that good. Same for blues.
Skill Order: U should max ur e first since it gives more dmg than ur snare.

Thats basically it, pls rework that and take some time to really think about those things.
Downvoting.

Edit: Longer buff duration>1gp/10
Good Hands 3/3 is also better than 2/3 and 2/3.