if you want to do this Flash [+[+word+]+] (the + marks are so the [ do not disapper)

I do, but i like building mejai's in peice's take the amplifying tome and speed boots on your first trip back, then see how you are in lane if your confident build into mejai's if not build into morello's or will of the ancients, never have a wasted mejai's and have options.

playing as a roamer Xerath is good in theory, but I usually mid with him, which limits roaming if i don't take teleport

Thanks for the catch, I haven't played much today. Its 1 o'clock and I'm tired. I've found that the void staff is essential since Xerath is a M.Pen char, after all it is part of one of his skills. I believe I am as dominant as I say I am, but also everyone has their off days in the game that's why if you ever do look at my recently played I do really well most games and then there are a couple bad ones. I do like how you did the math. I was planning on doing that later in the day today as it is 1:25 A.M now. My Mejai is delayed because it is more valuable when you can guarantee yourself kills with other items. I would rather have a Rabadons and void than a wasted Mejai because I couldn't secure the kill. Xerath as I need to mention in my guide more should be a roamer. Taking people unaware at long ranges and chilling in the back of team fights. Do you see where I'm goin with the late Mejai?

sry for double post but your skill sequence is also impossible you can't max arcanopulse at lvl 8 earliest is lvl 9

Void staff is only worth it if they have multiple people stacking mr, mejai's should be an early game purchase, one of if not first item, if your as dominate as you say you are it's better then deathcap early, cheaper, and just broken at 20 stacks.
you have roughly 35 flat magic pen between runes and items, %55 from masteries and void staff, and then the bonus from locus of power also % based, in an average game the average champ who can deviate from there build for mr will have 100, so 100-35 = 65*.45 = 29.25, not counting your bonus from locus of power, which is awesome, except when you consider everyone else with 50 mr, the flat is still very usefull, but everything else is wasted (50-35 = 15 * .45 = 6.75) so your 2300 gp voidstaff lowered there magic pen less then 8 points.

It took me a while to see if Mejai was worth it. As I kept playing and getting better I learned that I needed Mejai to guarantee anyone I faced would either be severely hurting and need to go back, or was just plain dead and another addition to my stacks. I didn't originally play with a mejai when I started out as Xerath. Its all a personal opinion though.

I don't know how to do that :/ help?

decent build but a wall of text,needs pics. absoloutely retarted to get mejais after all those spendy ones.