Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Skills are standart skills for mages + improved summoner spells
I use flash to escape or to bring myself to the right place to fire my ult. Clairvoayance is very handy to check bushes or to see where the enemy champions walk when they got 150 hp (or sth. like this) so you can kill them with your ult.
Items: first get dorans ring for hp + mana reg. and a little bit ability power (Buy also heal potion). If you can, then wait till you got 1235 and then buy mejas. if you have to go to base earlier, then buy amplifying tome, and when you got 350 or more but not enough for mejas then also boots. then wait till you got 800 and buy mejas. then the boots and a saphire or ruby cristal. build it to catalyst and then to rod of ages. after this, get frozen heart (first saphire cristal, then glacial shroud) for mana + armor (vs. meeles)and cooldown reduction. after this get guardians to survive longer. the last item is free but i chose Zhonyas ring.