@heLIXDARK i guess you don't play jayce that often? jayce is great BECAUSE he is very mobile, and with the boots of mobility you can literally shove a lane, recall, speed gate and be in lane before its even back to the middle. you can build other boots but i love boots of mobility on him. and for the manamune...try it. it turns into murasama or whatever when you get it to 750, it also FIXES the mana issue jayce has...therefore, when you do get it to murasama, you turn it on and your q starts to hit for more than 3/4ths of most champions health bars. try the build and then say its bad.

i dont undersant the boots of mobilty and the manamune its justbad no offense