Hello League community! The point of this quick item guide is to explain the importance of having a bulwark on every team that you play. Many players make the common assumption that bulwark is an anti-ap item that should ONLY BE BOUGHT if they have an OVERWHELMING AMOUNT OF AP. This assumption is incorrect. Runic Bulwark has one of the highest cost efficiency of any item in the entire game. For every 1 gold spent on Bulwark you get 2.41 gold in value. #Broken Much? -- So Basically if the enemy has at least one ap champion, this item is a brokenly op item to buy.

Pros:
Runic Bulwark gives the highest magic resist of any single item in the game.
The aura is godlike (and it benefits yourself as well).
The Bulwark has considerable armor and health as well.
The item can be built effectively on a top laner, jungler, or support.
Cons:
Runic Bulwark is expensive
The item is less beneficial when not near teammates

The next chapter is very dense and contains a lot of calculations, feel free to skip whatever your find to be boorish. I hope you learn something :)

This means that Aegis is a good buy EVEN IF you are not planning on joining teamfights (which you should). Aegis is considerably cheaper than Bulwark (800g cheaper) and provides an increasing cost efficient aura of 860g per person. Meaning that with 4 allies you receive 3440 gold worth of stats on the aura. The Aura alone is worth 1.6 times the cost of the item in addition to the actual stats the item provides for your champion. Talk about crazy gold efficiency! What's even more broken about this item is that you can buy this against ONLY PHYSICAL DAMAGE TEAMS (Teams with tanky jungler/support with 3 ad laners) and still have the best-in-slot gold efficiency item. Without the magic resist, the gold value for one person (aka yourself - including aura self-buff) is 1620g. You pay 2150g, meaning by yourself you wasted 530g. That is obviously bad if you are by yourself (top/jungle). As support the aura effects the adc. The weakened aura (860g worth minus 300g (subtracting the mr that we don't need)is 560 gold. That means as support against a full physical damage team, the aegis is still above the cost efficient threshold by 30g. So your Aegis is more 30g in lane and gains 560 gold per ally in a team setting. Thus if used correctly (you are sticking with your team) it remains brokenly op and worth the money. The gold value with 5 people benefitting from the aura against all physical damage is 1710g above break even. At a cost of 2150, you are getting almost 80% more than you paid for. Plus this theoretical Ad mid, Ad top, and Adc team would still do magic damage. Junglers and supports commonly do mixed ap/ad damage, and most champions still do minor amounts of magic damage even as adc/top/or ad mid.

Now lets get to the Bulwark. At 800g more than Aegis, the Bulwark costs 2950g. The Aegis is worth 2320 gold (for 1 champion) and the Bulwark is worth 2852 gold (for 1 champion). Technically speaking, you are paying 800g for an extra 630g in stats. So the cost efficiency is negative by 170g. But of course, that only takes into account the purchaser and not the allied champions that can potentially benefit. At a 200g value (1060g - 860g value of Aegis) per ally, the bulwark upgrade is a potential increase 630 gold above break even. You only payed 800g to upgrade it, but it is worth 1430 gold. --- IMPORTANT -- Note that the upgrade to Bulwark does not grant any armor however... If a guide tells you not to upgrade to bulwark against heavy ad teams then they are CORRECT, but for any regular game in the current meta (AP MID META) you would be strongly encouraged to buy the item. The upgrade gives the purchaser a bonus 50 health and 20 magic resist as well buffs the aura for an additional 15 magic resist. As you can see, the only useful stat for your 800g spent on upgrading the bulwark against a strictly ad team is 50 health. Priced at 2.64 gold per health, you payed 800g for 132g worth of health.

The goal of analyzing items so much is to better our chances of climbing the solo queue ladder or enhance our premade team's performance. This item analysis was made for you, the player, and I hope you make the best of the information I have provided. Thanks for reading what I have taken the time to write (Pardon for it being so dense).