Single-Target Magic Penetration?

[quote=Jebus McAzn]When taking an item such as Sorcerer's Shoes, Void Staff, or Haunting Guise, does the 20 magic penetration apply to all of your magic damage, regardless of who you're targeting? E.G., do all of these affect items like Sunfire Cape or auras like Mordekaiser's W or Amumu's W? If so, is the only advantage that Abyssal Scepter has over this magic penetration the fact that it lowers magic resist for allied champions as well? For the longest time, I've always been under the impression that magic penetration was always implying single-target penetration...[/quote]

[quote=caucheka]any source of magic damage is affected my magic penetration.[/quote]

[quote=B-Wong][quote=caucheka] any source of magic damage is affected my magic penetration. [/quote] Which is why people using mpen runes playing tanks usually get sunfires.[/quote]

[quote=Jebus McAzn]Thanks for clearing that up.[/quote]