Talk:Dragon/@comment-1920550-20150125044754/@comment-26231232-20150420160439

I thought they stacked additively, but apparently they stack multiplicatively. So, with Rabadon's, Archmage and the Dragon Buff (5 stacks) you get 152.88% AP. Relevant mathematics:

30%*5%*12%=152.88%

Now that I think of it, it's a ludicrous increase. In late game, in a reasonable build with Morello, Zhonya's, Rabadon's, Luden's, Void Staff and Sorc Shoes, plus the usual runes and masteries, you get 510AP from items, 22AP from masteries and 15AP from runes (flat AP quints) for a total of 547AP flat. If you have Baron and the Elixir of Sorcery you get an extra 80AP for a total of 627AP. The percentage increases bring it up to 959AP, giving you a whopping 332AP increase. It's insane. If you go full scaling AP runes you get 1063AP (368AP increase). With those runes, a fully stacked Mejai's and 5 Rabadon's (even though the passive doesn't stack) ANY CHAMPION can get 1475AP (510AP increase). It's insane.