Hi, I just became level 30, and I dont always win the game, but most of the time I do. Please rate and comment.

Pros
Good ganker
Good jungler
Good armor at beginning
Fast Movement
1vs1 Beast

Cons
Extreme low health in 5vs5
Dead when you are thrown in the air
Dead when you have stun or snare
is very annoying

For marks, I go with Greater Mark of Desolation
Master Yi has good damage but he also needs armor penetration to transport that damage.
For seals, I go with
This seal is for more critical damage, it can not be achieved by anything else except infinity edge. So this rune is really important.
For glyphs, I go with
It gives you a little attack speed and when you get phantom, it gives you a lot of advantages.
You do not need it that much though, since when you get ghost blade activated with your ultimate, it will reach highest point.
For quintessences, I go with
This is for that extra critical damage that we really want.

The only bad thing is critical damage runes cost a lot :(

21/0/9 Mastery
You can always change them depending on what you are getting for summoner spells.
But masteries in Offence is pretty much essential.

I start with . and 2 . I stay in my lane and usually do not come back until I have money to buy both , and . By level 9~11, you should have . Next, get .
is just perfect since it gives you that fast movement speed, crit, and attack speed. After that, I get for damage, then . If you do not have money to buy , then just get before . Now you make . Then I start building towards . Get crit items 1st!! Your game should be probably finished by now, and if the game still did not finish, get . In really late games I suggest you get . It really helps Yi chasing and helping team out. If the game still did not finish, sell , and buy . At this point you can even finish the game backdooring with flash.

For selecting skills, I get 1st. Then I select , it is because it gives you so much armor and magic resistence, you will be like a freaking tank when you use this, and it will actually heal your hp and not give you any scratches. When enemies are about to tower dive you, I use to get that high armor. Enemies like , when hes dead and about to use ultimate and you have red water dripping on your head, just activate .
After I take turns getting and exception of level 6, 11, and 16. When engaging team fights, you should always have ON.

I take to catch squishies, and to go through walls, escaping, and to catch up. If works for you, then you should get it, but is more convenient for me. When I am about to die during team fights, I usually use . When the enemies think I am gone, (since Yi is fast), I use to get some more hp back and engage back.

Please rate and comment, and feel free to correct me.Lol. sorry for playing Malphite in custom game, me and my friends were just playing around.
I hope you liked this build! ._.