Alright, I'm sure a ton of people have been complaining about the FoN (Force of Nature) being removed but I think I've come up with the perfect replacement. Basically it's a Thornmail for for magic resist. Make it from a Null Magic Mantel and a Negatron Cloak and you get an item that has the following stats:
100 Magic Resistance
Unique Passive: Gain a shield that blocks one enemy spell, this shield refreshes if you have not taken champion damage in 25 seconds.(kind of like the banshee's Veil)

I think this would be the perfect replacement for the lack of MR on tanky champions since the loss of the FoN

that just seems to be a better version of banshees veil; but a shield that often is a bit OP imo.

Force of nature was removed because it did its job of stopping burst mages to well. This item would make almost every AP mid in the game nonviable.

Force of Nature was removed cause it provided TOO much MR for a single item, armor is far easier fore-goable and in contrast to ad-champs, ap champs ONLY have their spells to do damage, that is why it is well justified that armor gets to a higher value easier, we CANNOT have an item with that much MR, that would hurt ap-casters too much.

Force of Nature wasn't even that OP, anyone who says it was doesn't know what magic pen is..

maybe returns 20% ability damage?

This idea has been brought up multiple times. It has a few major problems though:

Magic Damage and Physical Damage scale at different rates - Magic Damage mostly just scales linearly with Ability Power. Physical Damage tends to scale with Attack Damage, Attack Speed, and Critical Strikes. CDR and Magic/Armor Penetration help both out, but when it comes down to the mechanics armor just has to contend with exponential damage - while magic resistance doesn't. I'd say 50 MR more or less equals 100 Armor in the case of their actual effectiveness (except against Teemo and Kayle). 100 MR is stupidly high in that sense - Thornmail would be broken if it offered ~200 armor.

Also - the existance of Hexdrinker, Maw of Malmortis, and Banshee's Veil makes the unique way to redundant and unnecessary.

Magic Penetration wasn't terribly plentiful in Season 2, though Sorcerer's Shoes, Void Staff, and Abyssal Scepter were solid options. You needed all 3 to counter the MR from Force of Nature alone though - once it gets to the point you need three items to "counter" one it's not really a counter any longer.

if you play any modes like "Hide and Seek" then you realize how powerful Force of Nature can really be. Short of a full 6-item build, it's essentially impossible to kill anything that bothered to pick it up, even as burst-heavy APs like LeBlanc. The whole deal with playing AP in season 2 was mostly "don't focus the tank, ever" because you could actually build EHP against magic damage faster and cheaper than you could build magic damage. Pair regeneration and movement speed with MR, and you can survive getting bursted across the entire map.

The jungle was just updated to add more revenue and passive gold gains increased by 3 per 10 with season 3 - and most championship teams utilized gank-heavy tanks and rather solid DPSy bruisers both capable of getting a solid kill and assist score. Pair those things together, and the cost-effectiveness of Force of Nature is just to damn high - beefy champions don't need defense to be cheaper than offense, because they have ways to afford it and ways to get income close enough to offensive champions to no longer require much discrepancy in cost (or at least base enough stats and abilities that keep them viable with less gold).

Let's put it this way, yesterday I was playing a game with my friend who plays almost exclusively tanky champions, like Garen, the guy he was playing yesterday. Anyways he ended the game with over 300 armor and just about 90-100 MR. they had one Magic Damage champion on their team, well my buddy died three times in that game... can you guess which champion killed him, it was the AP champ. What's even worst is it wasn't even an heavy burst AP champ, it was fiddlesticks... Anyways I'm willing to bet $100 that if he had an FoN instead of a crappy replacement item for MR, like a scimitar or whatever he had, that he wouldn't have died ever...
The fact of the matter is that before this most recent patch a tank could tank any champion solo, now after it's either focus on beating out the ad champs or ap champs. if that team had two ap champs on it then we wouldn't have won... Tanks need an MR item that can compete with AP champs that get up to 600 ap with 20% or more magic pen. All i'm suggesting in this post is a possible solution, I honeslty wouldn't care if riot literally just gave and item that gave 75-100 MR. and just that MR



EDIT: In fact, without the scimitar and an MR item that gives 100 MR, he still wouldn't have come close to 200 MR, now can you tell me why that is OP?

This concept is inherently overpowered and will never happen.

MR is already too cheap, why should they make it better? Example: Bulwark