Items
- you don't have the Sorcerer's boots > you don't have the Sorcerer's shoes
- farm mins > farm minions

Skill Sequence
- to be more usefull > to be more useful

Summoner Spells
- someone that's full AP > someone who's full AP
- add that much too be viable > add that much to be viable

Laning and Farming
- you NEVER want to lane with > you NEVER want to lane against
- keenen > kennen
- vladmir > vladimir
- except to finish a kill > except to get a kill

That's it for proofreading I guess, not too many error so well written :)

Good luck with fixing!

^This sums it up

No

temzilla beat me to it

anyway, at like 3500+ mana, AA's Staff provides more AP than a second Deathcap

If you want the maximum possible damage on a target, use 4 Archangels staffs, 1 Void Staff, and 1 Rabadon's Deathcap.

5 deathcaps is just dumb.

down voting,

now heres why

Let me preface this by saying Karthus is my main to the point where I can junlge/solo top/mid/duel bot.

#1. Rabadon's stacking is very bad, yes it has highest base AP in game but the passive is not stackable. If you want glass cannon build (which are very bad on karthus but can be fun for pubstomping noobs) the best is stack archangel staffs. The AP passive is stackable so you will break over 1000+ ap with 6 staffs.

#2. Pure glass cannon is stupid, I know you have your after life and your ult will wreck face but remember your ult is NOT primary damage, and good luck in a team fight when even with your passive you only live a total time of about 2 sec then your 7 sec afterlife.

#3. your runes are a little off, going magic pen marks will help you a lot. also the only really trully viable seals in my opion are flat armor or flat mp/5. so i would use those instead of the ap all

#4. Your lane/farm section im really sure what to think about. First off there is literally only 1 champ to avoid that is Leblanc. However, if you must face her you simply take you wall at lvl 2 and through that where she flashed from to start with(that will shut her down pretty well). As for auto-attacking minions first then finish with lay waste you will be too slow early at farming the key is to place lay waste where it will hit only 1 minion so it does the double damage and you will farm just fine that way.

#5. Your team fight section is ok but you should mention late game your should be timing ult to hit as your tank iniates with the rest of your team, (unless your team sucks at clean up).

#6. summoner spells are ok i guess, though I would honestly bring clarity instead of ghost seeing as how you are slightly manna needy with this build and also if you are pushing your lane early to be ganked your kind of not playing karthus right. as for needing ghost latter its debatable I find it not necessary. (note this last point is not part of my downvote its just my personal preferance.

#7. also not reason for downvote but as mentioned and as you said you would be doing BBcoding is a must.

I will reconsider my vote if these areas are addressed and adjusted to a more reasonable build/guide. Feel free to PM with the link if you do make the changes.

have a good day, and good luck.

p.s. part of your problem may be that youve never played ranked so your not seeing the whole picture on how this is not full viable but things like that come with time and experience so dont let that bother you.

I understand that you think pure AP is not effective, but at 140 AP each even with no passive stacking Rabadon's Deathcap is formidable. I plan on adding BB code and pictures, like I said in the preface.

rabadon's stacking isnt effective...your guide isn't very detailed. and no pictures or BB codes. Try looking at other guides and improve your guide making skills. Not trying to be mean, i remember when my guides were like this. You will get better over time.