Is it any use combining Sorcerer's Shoes and void staff? [closed]

Question

While doing my different builds for my AP heroes, I've noticed existing builds on the net sometimes (often) combine Sorcerer's Shoes and void staff, and I don't really understand why.

When calculating enemy's effective magic resist, magic resist reduction and penetration is calculated in the following order :

1. Percentage magic resist reduction
2. Flat magic resist reduction
3. Flat magic penetration
4. Percentage magic penetration

Meaning that if you buy both item, Sorcerer's Shoes only give you 12 penetration if you have void staff. It even goes down to (a little more then) ten if you took the Archaic Knowledge mastery.

Another thing reducing usefulness of void staff is if the Archaic Knowledge mastery. Percentage magic penetration doesn't cumulate, both penetration are calculated one after another: meaning 40% (Void Staff) + 15% (Archaic Knowledge) penetration only gives a total 49% (and not 55%)

So question comes, is it still a useful purchase ? Problem is there aren't many items that reduce or penetrate magic resistance (Abyssal Scepter, Malady, Haunting Guise, Sorcerer's Shoes and Void Staff). Several options come up :

• Purchase both items (and more if needed)
• Concentrate on flat penetration and magic resistance reduction
• Don't take flat penetration (too concentrate on CD reduction or more AP) and buy void staff
• Try to compensate with runes the lack of penetration I may have if I don't take void staff
• Ask for teammates to take hero with spells that reduce magic resistance
• Anything else

I usually abandon void staff and work with Abyssal Scepter + Sorcerer's Shoes, but I'm starting to feel it may not be the best option.

Answer 1

For the most part I consider Void Staff to be an item worth considering only if my main targets (AP/AD carries, maybe even the support in rare cases) are stacking magic resist. Generally speaking you should just get Sorceres Shoes and then focus on building AP or other things... HOWEVER:

Some heroes are very much dependent on spell penetration - you can spot these generally from horrible scalings but high base damage. Brand comes to mind - when I play Brand I always rush Sorceres Shoes and Abyssal Scepter. From here on it depends a bit, but I generally always aim for Deathfire Grasp (mana regen, cooldown reduction + more damage) and then get a Void Staff. Brand is simply so dependent on penetrating through magic resist (his passive scales with spell penetration, but not AP) that you have to prioritize that over building tons of AP - especially when you consider that his scalings aren't that great.

I would say for most AP carries you will want the void staff if you're playing against a proper team as their AD/AP carries will get some magic resist at some point if you're doing your job right. However it should not be your immediate item to go for - especially as it is worth more the higher magic resist your opponents have (and they shouldn't have that much early on).