Talk:Magic penetration/@comment-74.5.61.216-20110111200635/@comment-182.55.236.10-20110703201311

mpen affects Bloodrazor and Wit's End (gives more dmg). anything which mred affects, mpen does too.

only difference is stacking copious amounts of mpen would NOT go below 0 MR, whereas high amounts of mred could give -ve MR (thus continuing to increase dmg per mred).