When should I be buying this item.. I always see myself rushing stronger AP Items like 
or even 
... Being the only AP pen item if i am not mistaken. When is this a good pick up? I usually only see it on a few champs 
Also I've always run 7.8 Magic Pen reds AP quints for my Mages.. but I was wondering if Magic Pen runes in quints or blues is ever viable too.
TL;DR is Magic Pen worth? or is AP generally better because late game 
anyways.
Sailor Mint2 votesIt's good on champions with very high base damage skills but bad AP ratios. While it's always strong early, it's not worth building on champions who cannot use Liandry's effectively.
Dreadlocks1 votesCould you name a few champs you would recommend getting it on other than the ones I listed? I guess 
and 
commonly get it too. But who else?
edit: why don't you see it on a champ like 
when champs like 
benefit largely from penetration as assassins. Also, why doesn't it give CDR >< lol
Sailor Mint1 votesYou see it on Kat and Kennen because it's a nice power spike and being manaless they can sometimes afford it. But Abyssal is probably better in AP matchups.
Champions with DoTs are great with Liandry (Brand, Malz, Rumble), same goes for certain poke oriented champions (Zyra, Vel'koz)
In the past, some assassins (i.e.: LeBlanc) used to buy Haunting Guise and sit on it. But right now Morellonomicon is just too good of a first item to even bother.
Dreadlocks1 votesSo are you saying its not worth buying most the time now? If we're going to talk about it being good on poke champs.. such as velkoz, how about ziggs?
Sailor Mint1 votesYou pick Ziggs for primarily for wave clear, not poke. You want to have enough AP to clear waves. Liandry's doesn't help with that.
In general, it's not a great item unless they have bad AP ratios. Or it's straight up worse than another more AP focused build path.
I'd go as far as saying that (almost) anyone who builds a mana item doesn't have room for it in their final build.
Dreadlocks1 votesFair enough, sooo... basically people only take AP Pen reds because 5.3 ap for reds is garbage... lol TLDR magic Pen is pretty useless unless you have a void staff
Sailor Mint1 votesIt's an amazing free stat (i.e.: on runes and sorc shoes), but you can't afford getting it in your six item core build over strong AP items.
The only options for marks are MPen and Hybrid Pen, depending on how much physical damage you deal. AP Marks barely give any AP and are a complete noob trap.
Dreadlocks1 votesNo I agree, its good to get early sorcs if you are going for kills.. which is why I was wondering why more people dont use or a more aggressive magic pen rune page.
Der Lindwurm1 votesThe health bonus is another big plus for an early haunting guise. And the AP and MP mean it's a good item to still good have while you're working on your real build. It mostly depends how urgently you need to rush something else.
Der Lindwurm1 votesZyra, definitely. I also get it when I play Leblanc and Morgana.
Dreadlocks1 votesMorgana's abilities do pretty damn good with AP, However, for Zyra and Leblanc.. Do you think Magic pen rune page would work? Perhaps exaggerated page of 20 Magic Pen -reds blues quints
Der Lindwurm1 votesI think it would be better to only use marks for magic penetration on rune pages and rely on items for the rest, but that's just me.
Reikken1 votesvoid staff makes flat mpen stronger
Nyaruko Chan1 votesIt depends. Do you like the idea of doing true damage to enemy carries who dont have much magic resist? If you have enough Magic pen your abilities start doing true damage to enemies which melts them. I normally like Spell pen on champs like dot champs like Brand, Rumble, and Mal because it just shreds people. Its also good for champs who need a cheaper build path to go down in order to get a faster power spike.