Talk:Heimerdinger/@comment-4878039-20120903132914/@comment-5052127-20120904174836

Also, not sure if i stressed this enough... always make sure you have enough mpen... if your targets have MR you aren't getting through you will be a lot less effective... Mpen scales on him like nothing else... you should see a MAJOR boost in damage as soon as you get sorc shoes

For him, even with NO other AP items... that 20 mpen, for 750 gold, adds AT LEAST as much champ damage to every one of his abilities as a 1600 gold big rod would have given him... that's pretty huge, and it's because all of his abilities damage comes mostly from the base damage.

He gets so much of his damage from his bases that he actually needs to get about 400 AP before his AP makes more than a 50% contribution to the damage of ANY of his abilities... this should tell you how important Mpen is to him... a close second for him is CDR, but he will have that capped with just Unholy Grail plus his ult and any masteries he has.