This is the only basic stat combination that doesn't exist within an item in the game
armor and AD don't have direct stat increases from an item, but AD synergizes with armor items like iceborn gauntlet and dead man's plate at least.
Athene's gives MR and mana regen.
We lost the old 
(which built out of Catalyst the Protector) due to 
.
I wouldn't mind having an MR and mana item for tanks again (since while I love Frozen Heart, I like Randuin's Omen more). I wouldn't say that it is needed, but it would be nice.
MR items are sort of lacking in the Mage department, especially for artillery mages. 
does not work well on artillery mages for those that are going to go herp derp on me.
Because of Ryze.
Why is there no item that offers mana and MR?
Probably comes down to 2 main reasons.
Life steal isn't found on items with critical strike chance for instance, despite that pairing being something every marksman would benefit quite heavily from. Health regeneration is mostly found on tanky items without armor, despite armor and HP/5 also having clear synergy. Movement Speed is found almost exclusively on attack speed items outside of boots.
Pairing specific stat combinations together like this tends to make item build-paths feel more distinct: like red, green, yellow, blue, and pink. If all stat combinations were possible most build-paths would feel more muddled and brown, feeling more like a generic level-up to all stats equally over pushing champions in distinct directions or forcing meaningful trade-offs within builds.
I actually miss Athene's being useful. It's an excessively niche item now, but that cup passive is very good; I just wish that it had something other than that shielding/heal passive that's effectively useless on quite a few supports who could actually use the item.
Mana and MR would be OP to have in 1 item.
remember Ziggs in s4? and it was only mana regen.
Don't do that again to us. No more!
