That thing you dont know about...
Forgive the clickbait title, seems to be the only way to get people interested... that and Yasuo/Lee Sin and inflammatory titles.
But I do have a thing some of you dont know about, its interesting to me, and I though it would be fun to share this concept. While some know, not everyone does.
What AM I on about?
The Ardent Pact build. Ok wuts dat? Well its a build where someone uses the Stoneborn Pact mastery:
Grants 5% maximum health as bonus health. Your crowd control effects brand enemy champions with an Earthen Rune for 4 seconds. Other allied champions who attack branded enemies heal for 5 (+ 2.5% of your maximum health) over 2 seconds (halved to 2.5 (+ 1.25% of your maximum health) if you are ranged).
And builds Ardent Censer:
Stats +50% base mana regeneration +60 ability power +10% cooldown reduction Passive Unique: +10% bonus healing and shielding power. Unique: +8% movement speed Unique: Heals and shields on allied champions (excluding yourself) grant them +20% - 35% (based on level) attack speed and their attacks drain 20 - 35 (based on level) health on-hit for 6 seconds.
Why would you do that, and if you did whats the point?
Well lets take 
as an example champion, or maybe 
if you prefer (tons of sups can do it, just examples use your imagination).
They both have CC effects that will proc the Stoneborn Pact (SBP) Earth Rune that will heal champs that aa them.
Ardent Censer procs grant atk speed and life drain when a champ is healed by the holder.
This means when you use a CC ability to proc the Earth Rune, the entire allied team can smack them and get the Ardent C. effects. This makes for some epic beat-downs. Now if youre wondering if thats really good or not...
Ardent Censer becomes 136.42% - 169.03% gold efficient if a single ally is buffed by its passive.
Ally Buff Value at level 1 20% attack speed = Gold 500 20 on-hit damage = Gold 500 Total Stat Value (1 ally buffed) = Gold 3137.67
Ally Buff Value at level 18 35% attack speed = Gold 875 35 on-hit damage = Gold 875 Total Stat Value (1 ally buffed) = Gold 3887.67
So yeah, when hits with her E, and roots a target, if all 4 allies were to aa that rooted champion, she would add between 12,550 to 15,550 stats to her team... like I said, "Epic beat-downs."
Now for those wondering... it isnt actually that amazing to be honest;
can (has been able to for a long time) R then E her team and do the same thing. 
can achieve the same effect for team-wide Ardent C. procs.
So 
also count to proc the Earth Rune for SBP. This means just about anyone can use the Ardent Pact build.
Want to see an odd example? http://www.lolking.net/news/stoneborn-pact-mastery-best-champions-special-interactions At the bottom it talks about the Ardent Pact Ashe support some of you may have heard about.
Now before anyone sees the outrageous item efficiency and power Ardent C. can have and calls for nerfs... keep in mind have been doing this for a long time, and you havent noticed.
Anyway, Ardent Pact, thats the thing you dont know about...