Why Morg's W and Passive are outdated, and some good suggestions for what they could be

There are several big issues with her passive and W, and they just don't work well with all the changes that have lead to the current state of the champion.

The strength of her passive was entirely reliant on her W-- the Spellvamp wasn't enough to work well with her Q or R, but because her W could be placed on an entire minion wave she could sustain in lane against champions with better poking abilities. Now, however, several changes have been made that make her passive pointless:

1. Mage Supports (including Morgana of course) are now adjusted around their role as Support first, with Mid as an afterthought. So instead of having her abilities be powerful enough to give her reliable healing, they're made weak enough so as not to completely oppress bot lane.
2. Will of the Ancients was removed, giving her no workable option to build for increasing her Spellvamp.
3. Her passive itself is actually no longer Spellvamp, but a pseudo-spellvamp that lost its strongest application. Since it no longer applies to damage dealt to basic minions, she can no longer use a minion wave to sustain herself in lane.
4. Spellthief's Edge now only grants gold once per cast of AoE or DoT abilities regardless of how many enemies you hit, which is a problem because her W is both and was the main way she received gold from Spellthief's.

I hope this makes it clear that these two aspects of her kit are relics from a bygone era of League. Unfortunately, none of these changes could be reverted if they want to keep her as a support. The first problem has to do with an entire class of champions, so it couldn't be dealt with unless Morgana was made into another class, effectively making her not Morgana. The second problem couldn't be dealt with because WotA would cause even bigger issues for other champions. The third problem is linked to the first, because Riot has judged that use of her passive as unfit for the Support role, despite the fact it's perfectly fine for a solo lane. And likewise, to change it would require changing her class, which barring a full rework could only be done by removing Black Shield's ally-targeting ability. The fourth problem, like the second, can't be reverted because of other champions. Brand and Zyra also deal multiple ticks of damage with single abilities and benefited far more from it than Morgana, but because she also used that method she was punished alongside them. Reverting it would mean bringing back what was a bigger problem for more champions.

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I don't really know what they would go with for a new passive and W, but here are my suggestions:

Passive: Veiled One's Justice Enemies who attack Morgana, or an ally being shielded by Black Shield, take 10/20/30/40 (+15% AP) (+5 per per 1% Heal and Shield Power) Magic Damage per instance of damage. (increasing at levels 6, 11, and 16)

(With a full build at level 18 , that would be 97 damage per instance. For comparison, Annie's E deals 60 base damage at rank 5 before even considering its 20% scaling, in addition to the damage reduction. So I feel this is a perfectly reasonable amount, if not actually a bit too low)

It would give her more damage, but not in a way she can abuse by being overly aggressive, and it would synergize with her E, giving her more interaction with allies. It also fits in with the character, punishing enemies for their crimes.

W: Burning Anguish Effect Radius: 1200 (to encompass her Q and R ranges) Cost: 70/85/100/115/130 (Relatively high) Cooldown: 8 (Since it has a somewhat difficult cast condition) Passive: Enemy champions made immobile by Morgana, or an ally shielded with Black Shield, gain the Chained debuff.

Active: Morgana sets all Chained enemies in the area ablaze, ending any current immobilizing effects on them, but slowing them by 20% for 3 seconds and dealing 12/24/36/48/60 (+25% AP) Magic damage every half-second. (Total damage would be 72/144/216/288/360 +(150% AP), which is about on par with the damage from standing in her current W for the entire duration. Keep in mind that a normal build for her only has 110 AP at full build, which would converts to only 165 damage.)

This would give her more interaction both within her own kit and with allies, and allow for great skill expression to separate the bad Morgana's from the great ones in a way other than just landing Q's. The fact that a you'd have to trade off hard CC for the damage would mean you might accidentally give the enemy a chance to escape, but a well-timed W will mean you get the slow on top of the full duration of yours or a Black Shielded ally's hard CC. And the really great Morgs will be able to properly utilize it by shielding their front-liners before an engage.