Guardian is your ideal tanky support rune. If you have an ally that you need to protect, this will help keep both of you alive and powerful. As long as you can keep close and body block, this should keep your AD Carry nice and safe.
What does it do?
When you’re especially close to allied champions, you will guard them. If you cast a spell on them, they will also be guarded. When champions are under the guard effect, taking damage (either you or them) will grant you both a powerful shield and movement speed boost.
Which runes go well with it?
Guardian is built for your already beefy friends. As a result, we are going to focus on increasing our tankiness and sharing it with our allies.
Font of Life is easily the most obvious choice here. The goal of most tanky supports is to drop CC on the heads of your enemies. Since you should frequently be roaming with your ADC, offering up some extra healing for them when you are far away is a great trade-off.
Laning is often times a long process in games. Conditioning will offer you free stats that you can immediately take advantage are, as long as you are paying attention. The moment it hits 10 minutes, you can engage with some extra powerful tank, throwing everyone off guard.
Speaking of laning, a lot of minions will be dying near you as the game goes on. Whether you are following your AD around to soak experience or pushing a wave with other allies, Overgrowth will keep offering you free stats. Since supports are usually pretty poor, free stats are beautiful.
Inspiration will be our secondary tree. We are going to increase our movement speed here, helping us stay fast throughout the game. Magical Footwear will make our 10 minute boost from Conditioning even more powerful. Approach Velocity will help us follow up on our own CC or save an ally in trouble.
Who’s it for?
Guardian is for the bodyguard-style supports. If you are running an AD like Kog’Maw that needs extra peel and help, bringing along one of these beefy friends will help that void puppy stay alive. Taking Guardian will only make life easier.
You want to take this rune on champions like:
Braum seems to be the best champion for this rune, as he is always able to escort an AD Carry to safety. Rakan may seem a bit squishy for this but his kit is perfect for Guardian. In a similar vein, Thresh players who take Guardian will have to be far more aware of how they use Dark Passage.
Champions like Leona, Blitzcrank and Alistar may come to mind, but runes like Aftershock would actually work far better for them.