Mana + Magic Resist?
I'm sure there's a good reason, but why can't these stats both be on the same item? I cannot count the number of times that those were the only two stats I needed. :(
I'm sure there's a good reason, but why can't these stats both be on the same item? I cannot count the number of times that those were the only two stats I needed. :(

You can get manaregen+magic resist. Which champ are you actually playing?
I could imagine a number of reason. Though I would think that the most likely reason is that most champs, wouldn't really need mana and MR on the same item. And over all, most champs would prefer MP5 over Maximum mana, where we already have the chalice line of items.
Back before his rework, Ryze commonly built Frozen heart, after he finished his tear and RoA. And this made him fairly tanky while having scaling damage. And a lot of people didn't want another defensive mana item when Ryze could build that tanky.
Most mages probably want the spell slinging benefits of MP5, so it would be mostly caster tanks that would build flat mana. But for defensive purposes, Tanks would rather get a Frozen Heart or a catalyst, and wouldn't need more mana after that.
If there was one only ryze would get it. Any other champ that get it would only be paying for the MR which if you want MR then just get another item.
Mages won't get it because mana scale for shit late game which is why mana items are so cost effective.
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