Is Void Staff always effective, or it's meant to be situational?
For almost every ap mid I used (spell-based, like Annie) I bought the same thing: boots, rabadon and void staff.
There're certain moments where I start asking myself... Would it be more benefical in all situations to get even more AP, or is void staff still the best option even if almost no one buys magic resistance?
However I always feel safer to get void after rabadon, as it guarantees there's less chance of survival for them against my champ's spells.
3 Answers
Trade in Void staff for more AP? Hmm no.
Trade in Void staff for more Utility? Yes definitely!
Void staff is a pure damage Item. The item is usually purchased because Magic resist Items are pretty common in the current meta (especially GA and Banshees). The Void Staff itself is becoming really effective after an opponent has over 100 MR, since yours spells will then deal damage as if he has only 65 MR. It increases your damage over all, even with opponents that don't have MR items.
Now as already said, Void staff is a really important Item for every AP Caster and you should buy it on everyone who deals mainly magical damage. You can however wait with buying it. With most (not all!) AP champions your Item path should be -> Core Item (different from champ to champ), Boots, Rabadons, Utility Item, Void Staff, Situational offensive/defensive item.
For Annie I'd say a good generic path would be: Rod of Ages/Deathfire Grasp -> Boots -> Rabadons -> Zhonyas -> Void Staff -> Abyssal
Of course you shouldn't build like that every game but It's a safe build if you don't fall behind too hard. Also if you see that you won't deal any damage because the enemy team is stacking MR, Get the void staff earlier.
The most Important thing about void staff (and rabadons aswell) is that these Items scale with AP. If you rush them too early they won't be as effective as other Items. This is why you usually get Rabadons As a Second AP Item and Voidstaff as a 4th or sometimes 3rd or 5th.
Also a thing to mention: If your opponents really build no MR at all (which is rarely the case), you can also rush a Liandrys Torment/Abyssal. Different from % Penetration, Flat penetration/Flat MR Reduction can really put you ahead early, even without that much AP.
3You want to get void staff if they are building a lot of Magic Resist. I usually build it on most midlane champs due to the fact it helps all your spells do more damage. It shouldn't be built early because there are many more viable options early but in the late game it becomes extremely viable. Nidalee would be one you would want to get it right after rabbadons deathcap because it makes your spears hit even harder. You rarely see an adr without Last whisperer for the same reason.
that would mostly depend whether your having a hard time against enemy champions and you're skill set. i'll focus on the champion that you mentioned here, which is annie. void staff is generally a good item especially you have rabadon before you get void staff, although yes it would be better if you get abysmal IF no one is really getting m.res in the opposing team. also annie is a burst hero that must lay down everything she's got in the first few seconds of a team fight.
