Zilean, the Chronokeeper

Zilean, the Chronokeeper implements time-themed abilities to harm or slow enemies, and to aid allies by speeding them up or reversing time to a point before their death. His most useful ability is his ultimate that can prevent the death of an ally, returning them to life shortly after for another chance to fight. Depending on how he is built, his time bombs can devastate opponents by causing AoE damage. Building him with cooldown reduction is the most effective route as that combined with his rewind ability causes cooldowns to be nearly non-existent. 

Lore

 In the wastelands of Urtistan, there was once a great city-state. It perished long ago in a terrible Rune War, like most of the lands below the Great Barrier. However, one man survived. He was a man obsessed with time, a sorcerer who dwelled in the giant Clock Tower of Urtistan named Zilean. As the Rune War devastated his homeland, he experimented with powerful temporal magic that he hoped would bring peace. Instead of perishing with the rest of his kind, Zilean survived and was afflicted with chrono-displasia. This mystical disease made him immortal, but also made him detached in time. His consciousness now drifts through time, from any point he has already lived to the present. Zilean's greatest curse is that he sometimes experiences Urtistan as it once was and the rest of the time resides in its lonely ruins. The Chronokeeper has joined the League of Legends hoping to either find a cure for himself or a way to bring his people back from the past. 

''The Chronokeeper is never in a rush. He has all the time in the world.''

  Abilities ( /'s seperate the effectiveness of each level of the ability in question )

   

Heightened Learning (Passive)

Increases experience gain of all allied champions by 8%. 
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Time Bomb

Places a bomb on any unit, allied or enemy, which detonates after 4 seconds, dealing area of effect damage.  
Deals ( 90 / 145 / 200 / 260 / 320 )[ 90% of ability power] damage to surrounding enemies. 
Cooldown: 10 seconds 
Cost: ( 70 / 85 / 100 / 115 / 130 ) mana 
Range: 700  
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Rewind

Zilean can prepare himself for the future, reducing the cooldowns of all his other abilities.   
Reduces the cooldown on abilities other than rewind by 10 seconds. 
Cooldown: ( 18 / 15 / 12 / 9 / 6 ) seconds 
Cost: 50 mana 
Range: N/A 
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Time Warp

Zilean can bend time around a unit, altering their movement speed for a short time. 
Slows an enemy's or increases an ally's movement speed by 55% for ( 2.5 / 3.25 / 4 / 4.75 / 5.5 ) seconds. 
Cooldown: 20 seconds 
Cost: 100 mana 
Range: 700 
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Chrono Shift

Zilean places a protective rune on an allied champion,  teleporting the champion back in time if he takes lethal damage.    
Marks an ally for 7 seconds. Should they die in that time, they are returned to life with ( 600 / 850 / 1100 )[ 200% of ability power] health. 
Cooldown: ( 180 / 180 / 180 ) seconds 
Cost: 200 mana 
Range: 900 
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