Zilean's Time Bomb is the only ability in game that doesn't scale linearly, meaning that the increasing damage given out for each rank in the ability is potencially different than the previous one.
After the base damage of 90 at rank 1, Rank 2 and 3 give 55 damage, while 4 and 5 give 60.
Zilean's concept may be inspired by the fictional personification of time, Father Time, who is usually depicted as an elderly bearded man, dressed in a robe, carrying an hourglass or some other timekeeping device.
The main character, Billy Pilgrim, discovers that he randomly jumps between different moments of his life, but is unable to change anything that has happened. He relives his life at random intervals from birth to death for all eternity.
When Zilean is in a match where an enemy Volibear is present, he gets a buff called Armored Bear Hater.
This icon reads: "In my day, we would never have allowed an armored bear into the League of Legends."
Volibear also gains an icon when Zilean is in the opposing team. Allied Volibear is unaffected.
Additionally, if the enemy Volibear kills Zilean, he will remark "I have a special claw for you, Zilean" or "Your time has come, Chronokeeper."
This is a reference to Zileas, who was against the possibility of Armored Bears on the forums.
Zilean is the first champion to have a non-ultimate ability which can not be ranked up at level 1. The ability is Rewind, since Rewind can only be used to reduce other abilities' cooldowns, making the spell useless if ranked at level 1.
Zilean was the first champion to be released after initial release.
Zilean joined the League to find a cure for a disease called chrono-displasia, and to save his people.
Zilean constantly consults Ryze, for using summoning magic, similar to magic that summoners use, to find a cure. Ryze stated that they are close to the cure.
It was Zilean who developed the temporal stasis bubble that halted the war in Kalamanda. The high amount of magic used for the bubble also led to the awakening of Skarner.
Due to the fact that the Riot design director, Zileas, was adamantly against the implementation of armored bears, Volibear and Zilean dislike each other.
During his investigations on Valoran, Vel'Koz and a few other voidlings came across the now abandoned Urtistan, Zilean's birthplace and former residence, eventually making his way into Zilean's tower. The voidborn discovered very advanced pieces of technology, believing its owner to have undiscovered knowledge