Seriously, it's insanely strong - gives huge AP, lots of survivability, and a ridiculously strong passive that complements every ap carry.
I can't think of one champion that shouldn't get it, maybe even as a second item.
Sinneli2 votesI'm building it on Brand and watching more burns and slows. But it's a bit of a trade. Let's say I'm playing Lux. Now i have to ask myself. I have 3000 gold from all the farming. I'm a Lux. So do I want to participate in teamfights and creating large zones that will slow for 1 second if I hit people, thus allow myself to contribute more to team utility? Or do I want to buy Luden's Echo, which offers me more movement speed instead of health, and instead of a slow, increases my overall damage output with 100 + 10% more AP on the ratio? Note that this 100 difference will make a difference for an execute damage sometimes. Unexpected burst can occur.
So they have to choose, I suppose.
And some people just want damage more than utility.
Unless you are playing Brand. In which case, slows for all eternity as they writhe in the flames of LIandry and your passive.
Reikken2 votesno idea I always build it. even before the buff
MeltedBlock1 votesExpensive, expensive build path and some champions need specific 6 items.
Dracid1 votesexcept it is by people who know better. It's still a fairly new change so most don't realize it.
Binxy Prime1 votesMost mages need mana regen, then once you have that and CDR from Morello or from Athenes then you need to get damage or you can be ignored in fights, if your team has a lot of damage already like riven top or an assassin jungle or your team has a ton of aoe and you just want to pick off straglers then Rylais is pretty strong early. In general your second item needs to be rabadons or ludens for damage. After CDR + damage item you will start needing pen to be able to damage since most tanks stack armor right now and the enemy team will have an aegis for sure unless they are bad. You could then consider getting Rylai as a 4th item but if you really need survivability you probably go for zhonyas. Its a pretty good last item though and was even before the buffs.
TheDuelist9991 votesI actually started rushing it on cho the day before the item changes and then afterwards i was like oh ya baby. I build it on cho no matter what edge of the ap-tank spectrum im planning on by end game. W silences and slows enemies literally cant dodge q except for maybe yii. His e empowered autos slow so if you get the edge up in a fight there is no escape for the enemy.
diamondlight1 votesrylai cho is beast mode
Marthian1 votesBasically 6 item slot syndrome: There are some champions that will have no issue building Rylai's, but there are others that need those slots for mana, cooldown, or other utility (Zhonyas, Luden's, Rod of Ages.)
Slamurai Jack1 votesBecause Rylais has the same problem it's always had; what do you give up for it? Deathcap, Void, a mana or mana regen item, Zhonyas, boots, and Ludens are core on pretty much every AP carry. Realistically, it makes the most sense to give up Luden's for it, but good luck actually getting people to do that. I know I won't.
Turret491 votesSometimes it's entirely unnecessary and mana/sustain is more important. 
LankPants1 votesIt's a very good item, but claiming every mage should build it is incorrect.
There are a lot of mages who just have a low synergy with it like , 
and 
.
Titanium701 votesWell two main reasons:
