I honestly don't get it. They were both the exact same item except one was for AD and one for AP. Even with the new starter item for it 
, I don't see Mejai's anymore than before it got it. Maybe I just don't get it cause I'm just a bronze scrub, but I see no harm in keeping Sword of the Occult.
The big difference I see is in how the items were actually used. Mejai's is used by champions that stay back and try to avoid committing to fights. It lets them do more damage if they stay safe. Sword of the Occult was used by assassins that used it to instantly burst someone down before they could possibly react (The whole "rengar out of stealth killing you in 0.25 seconds idea"). It could be that Riot is more comfortable supporting the long ranged positioning-based risk playstyle than the short-ranged instakill-before-reaction playstyle. Mejei's could be a legitimate option, while Occult was just stomping harder if you were already stomping.
I don't like the items. They seem cursed. Any time I see someone buy one they never do well after.
The problem with Sword of the Occult is that... well... it just doesn't work.
Thing is, there are three kinds of champions who would buy Sword of the Occult:
AD Assassins Damage-Oriented Bruisers Marksmen
Marksmen wouldn't buy it, because they're always the priority target in every game, and are super-weak at the early phases, meaning that they're probably going to be losing stacks constantly, specially if they sink money into something that takes a while to get rolling instead of something more cost-effective from the get-go.
Damage-Oriented Bruisers just have more important, better items to buy, since they require a mix of both defense and offense, and thus, have to balance their itemization very carefully and can't waste it on an item that isn't even going to help them snowball all that much. Plus, they're constantly on the frontlines, which raises the chances that they'll get killed.
And AD Assassins are very much sink-or-swim champions, who even when they're ahead, can very easily be halted by one good play and killed. Thus, they do not need to tack on extra risks to get more of something that they already have enough of.
In comparison, champions who can buy Mejai not only scale better with AP, but have better ways of acquiring stacks (Such as AoE abilties or utility to rack up assists) and are overall more safe than champions who are constantly putting their necks in the line.
lets talk about the old hp stacking item rip
dunno I never saw anyone build Sword of the occult vs once in a full moon for Mejai's (Usually Lux or an AP support)
So ADCs don't buy it for free stats.
i personally love 
on 
its really easy to stack and gives me enough ap to almost match the amount of ap normal mid laners get i mean it was a big gamble but now it feels easier to stack plus the passive to helps me get even more out of my potions then i already do with the 
.
Mejais has niche uses on Lux/Janna and the new passive is pretty great too. Occult was 100% always a trap item with no ad champ that can really 99% prevent their own death through smart positioning like Lux/Janna can.
Honestly though I wouldn't mind if they got rid of both since outside niche scenario's, mejias is a trap most of the time too.
If sword of the occult was promoted too, then the AD champs would be even more snowbally. Everyone would complain more.
On the plus side, 
can't buy it ¯_(ツ)_/¯
im guessing cuz of the ad buffs. so many new ad items and strong ad champs popping up, adding in occult would just make the snowballing so much more intense and the opposing team would have way too tough of a time to stop it.
they are probably going to rework it, and bring it back as a different item. Kinda like what they did with the ad grievous wounds.
Mejais wasnt promoted,it was reworked.
So you should be asking why wasnt SOTO reworked as well.
Because it isn't as effective on fighters as mejais is on mages,due to fighters having to get up close with a higher chance of dying. It had no possibility of being used in your average game while mejais still works,but rito wanted mages to choose between damage and support cooldowns so the cd was removed from mejais.
Because rito knows they made AD champions op so to reduce an even greater snowball they removed sword of the occult.
Riot took away fun champ Friday i did with my group.. rules where simple.
-call your role
-call AD or AP
-last 10 secs of selecting a champ start spamming the random champ button ..
-build either or sword of occult first
-play game ..
Personally I figured it was Riot Promoting builds with more AP and less AD.
Noob traps.
They basically reworked Occult into the new item Cull. As others said, AD champs can't really keep those stacks unlike long range mages, so they are better off with getting extra gold for their core items via Cull.
I build SotO on Akali.
Mejai's was overall nerfed, not promoted. It was balanced to be a more usuable item rather than an "I'm ahead" item.
Mejai's has it's place in the meta, to the point where it actually shows up in recommended items for champions. Safe AP supports like it, long range Mages, snowball mids. With occult, even being ahead didn't mean you'd buy the item. Occult would give a large amount of AD if ahead, but Brutalizer gave cdr / armour pen, tiamat gave wave clear, yomuus gives movement speed.
Cause SOTO was in a bad place where as Mejais can be used in mid or support to rack up its stacks.
They could make the cull go forward into the sword of the occult?
Many long-range AP mages and supports built Mejai's because their long range meant they could throw out spells safely. AD champions, on the other hand, are a common focus for the enemy team.
Mejai's and Occult both are high risk high reward and same goes for Leviathan which was removed a while ago but gave health and when maxed out reduced damage being taken by 15%.
If you are able to fully stack one then you in turn have basically snowballed an already strong advantage to be even better.
I guess the main reasoning for keeping Mejai's is that it is the one most liekly to result in lossing stacks if you mess up since only champs like LeBLanc and Lux seem to get it. Annoying yes but if caught out often easy to kill and in turn stop the item from snowballing.
Also the fact that SotO is 110 AD if maxed out and there is kinda a lowering of AD on most items.
Really wish they would make rengar lose trophies for his deaths so he has to be played consistently well in a gem to keep those advantages.
Sword of the Occult was my kha'zix pentakill starter pack
