This is my first champion build, but I can assure you - this type of Janna is a horrifying opponent. I'd like to start off, that this Janna requires excellent timing and awareness. She can absorb countless damage, by keeping her shield up almost all the time and she also can kite and slow opponents, while outputting a lot of damage. In addition to that, she retains her old escape mechanisms.

You might ask: Why armor penetration? You see, this whole build is centered around attack speed and penetrating as much armor as possible, as you already gain damage from your shield spell. Since this build will not cap your attack speed, it is recommended to get as much as possible from runes, while also taking some armor penetration.

Nothing to be explained, really. You just don't need defense due to your shield spell, but you must take at least the attack speed and armor penetration from the Offense tree.

These items reassure that you have a MAXIMUM cooldown reduction. In addition to that, you also gain a double-slow and lots of attack speed with a little bit of lifesteal and ability power to keep you alive.

You may ask: Why Heart of Gold and Avarice Blade? You see, I tested it and these two stack. Get these early game, and you can gain piles of gold very quickly. In any case, Avarice Blade is needed for the Ghostblade, so you will have to take it anyway.

As for Heart of Gold, once you run out of space for the last item I recommended, just sell it. It will have it's job done by then.

Zephyr must be taken first, so you can easily get to your position and avoid first blood, which usually comes from all sorts of Crowd Control spells. The shield is leveled on later. Remember to keep the shield on yourself most of the time, even when you attack, it's essential to shield yourself for bonus damage.

Monsoon is a not-so-needed spell for this build. You will stay back, yes, but your speed will allow you to easily escape. And apart from some mild healing, all you will need from Monsoon is the knockback - which combined with Howling Gale let's you easily escape and survive.

Ghost is the most needed spell. You will already have 2 speed increases - Ghostblade and Zephyr. But sometimes, you might also need Ghost, as some people just stack Phantom Dancers and easily catch up. As for Flash, combined with Monsoon and Howling Gale it can prove to be one of hella-many escape mechanisms that you have.

However, you can always replace Flash with Teleport, which would allow you to sustain lanes much easier. But then again, it's up to you to decide what spells you want.

Pros:

Even more escape mechanisms.
Extremely high speed.
Doubleslow (Frozen Mallet and Zephyr).
High Armor Penetration.
Maximum Cooldown Reduction.
Semi-High damage.


Cons:

Team cannot depend on you to heal or shield allies most of the time.
Exhaust and Attack Speed-Reductions can cripple you.
You are vulnerable to Casters.

This build cannot help your allies most of the time with the shield and Monsoon, however, any chasers can be very easily slowed to allow your allies to escape. You can also knockup and knockback enemies, which can create great situations for your team to use.

This is by far a VERY rare build, but I assure you, it's extremely efficient. The uniqueness is that you can gain by far one of the most crowd control spells in the whole game. In addition to that, your slow are simply crippling, disabling your opponents due to extreme speed reduction.

All in all, this Janna is very tough. She has a fair amount of health, a shield, two slows, a knockup, a knockback/heal and extreme amount of movement speed. It is not tried out, but I think she can even jungle, but that would be a different build, resulting in starting with the shield and taking Zephyr at level 2.

I hope you enjoy her.