Sylvanus, the Quintessential Support

Sylvanus is the Guardian's Guardian. All of his abilities are perfect for feeding your teammates, controlling your enemies, and keeping yourself (and your team) alive. He is one of the most underrated Supports in Season 3, and there is some good reason for that. He can be slow, awkward, and difficult to use. His abilities reward skillful aim and timing; likewise, they can be quite punishing if used improperly.

Sylvanus' Strengths
High Crowd Control
Can pull enemies
Mana and Health Regens built into kit
Can feed a teammate kills effortlessly
Reasonable Cooldowns
Excellent Sustain
Hard to kill
Ranged Auto-Attack, with area of effect damage

Sylvanus' Weaknesses
Bulky, can body block teammates just as easy as enemies
Poor wave/camp clear
Auto-Attack is slow, and takes getting used to
Enemies that get too close are hard to hit
Abilities have small hitboxes, making them easy to miss
Direct damage is poor

After some testing and tinkering I've made some changes to the builds and labeled them more appropriately. I will make some videos to better describe them in detail, as well as some more thoughtful descriptions in the guide below. This is going to be an undertaking as I get the numbers and theorycraft settled.

Coming Soon...
I have a few "loose" guides, but I will make a more thorough guide soon.
Click here to see my Channel

In the Early Game, Sylvanus is strong. Wisps and Verdant Growth will give you and your Carry an amazing amount of sustain. With skillful use of Verdant Growth you can almost assure your carry First Blood by catching the opposing Carry off-guard, and rooting them into a quick death.

Make sure to leave a Verdant Growth flower under your tower to allow your Carry to regen Mana between minion waves. Additionally, you will need to think of Wisps as a Heal, and not a source of damage in the early game. This is an important mindset to be in, as Sylvanus is not going to do much in the way of damage in the Early Game. Keeping your Carry healed up, and fed, is your sole job!

Wards, Wards, Wards!!
Sylvanus will be slow and lumbering. He will also be in the way. A lot. Use Wards to keep your vision around your lane, because you can not only get caught off guard; but you can also get in the way of your Carry trying to escape. When you see a gank incoming, you can use your bulk to get in the way, providing excellent peel.

About Nature's Grasp
Most guides will tell you not to worry about his 3rd ability. I consider it to be REQUIRED on level 3. I can't tell you how many times I've saved my Carry from aggressive opponents, and ganks, with a well timed Nature's Grasp. Not only that, but if you are pushed under your tower, Grasp can snag your opponent into the Tower range and when followed up with a well placed Verdant Growth, can gift wrap a kill for your carry in seconds.

Nature's Grasp is very hard to use. No one will argue that. That said, it's difficulty is not a reason to ignore it. I use it frequently. Even when you miss, it tells your opponent that you are trying to grab them - that will cause them to behave accordingly. This will put opposing Supports back on their heals, as they don't want to get pulled away from their Carry, and likewise it will make the opposing Carry much more timid about rushing in.

In the Early Game, Nature's Grasp is the best way to keep your opponents on the heels. Use it. Often. You will miss the Grasps you don't make 100% of the time. Even if you only land 10% of them, that 10% will be meaningful.

The Mid game is marked by the acquisition of your second Relic: Blink. At this time you can safely sell your Watcher's Gift, if you want. I usually do, since I will spend a lot of time moving around in the jungle, between lane assists. You will grab more than enough exp/gold from babysitting lanes, ganks, and proxies. I know many disagree with that, so you-do-you on that one.

Blink allows you to initiate with your Ultimate ( Wrath of Terra). This is a game changer, and at this point you will be able to more freely rotate around the map. Using Blink-Wrath to catch opponents off guard will create an imbalance in your team's favor every time. It also causes your opponents to react to the sight of you.

Wrath of Terra is devastating. It is a knockup with a 5 second damage over time poison that ticks every second for 5 seconds. While the scaling is not great (25% Magical Power), the effect it has on the other team's psychology is.

The real power of Sylvanus is psychological superiority. In the Mid Game, this is where he begins to truly shine. By the Mid Game your Wisps should be maxed, which makes you a more effective team fight healer than Ra, Aphrodite and Chang'e. Using your Wisps religiously throughout team fight engagements makes your team very hard to kill.

The overall psychological impact of having Sylvanus around is noticeable. Teams are less likely to engage on even ground. They are less likely to chase. They are less likely to commit to a gank once he shows up.

The psychological effect is made even worse by the Blink-Wrath combo, since he can just appear out of no where, drop his Ult, throw Wisps on you, and then root you in place for a teammate to pick up - all without stopping, as he progresses to the next lane, to gank your friends.

Mid Game Sylvanus is a terror.

Pro Tip
When rotating between your team's lanes, be sure to drop a Verdant Growth flower under your laner's towers. The MP5 is still helpful.

Also, be sure to use Wisps as you pass by your teammates, or leave your base. Topping off their health can save a potion, and every little bit can help get them online faster.

Late Game Sylvanus is not as potent, but his psychological effect is still very relevant.

Sylvanus will once again fall back into his healer role during the Team Fight Phase, but now he will be capable of tanking Towers, and Phoenixes. Sylvanus can easily hold down most objectives, keeping the team healed up and providing a decent MP5 boost (though it is not as helpful as it was in the Early/Mid Game).

Blink-Wrath initiation will be your hallmark at this point. The opposing team will come to expect it, but there is little that they can do to prepare for it. Wrath of Terra will cause panic, chaos and frustration across the board. It will burn beads and sanctuary relics, and break-up a team formation just in anticipation of it.

Remember to use Wards, even in the Late Game to watch your back, and to get vision around corners. Once you hit level 20, and have a full build you can solo towers with Wisps active. You can tank Phoenixes with just a single teammate and no minions. Take advantage of this and you can effectively split-push your way to the enemies Titan.

The Late Game has its problems though. Once your opponent's ADCs are online, your tankiness can be mitigated by penetration items, crit damage and protection debuffs. Nemesis can be particularly detrimental. Just rely on your superior crowd control abilities, healing over time, and let your team worry about securing kills.