Jansen Tembreck, The Man From Nowhere

Jansen Tembreck would be a Support, focusing mainly on cooldown reduction and slows. His passive would be a "paired ability" like Kalista's Black Spear that reduces the cooldowns of the champion who lanes with him by 10%-25% depending on level.

Passive: Anchoring Memento. Jansen starts with an item called Anchoring Memento, which reduces his cooldowns by 10%-25% depending on level. Using this item casts it like a ward, and a nearby allied champion can pick it up, gaining the same benefits while removing Jansen's. Once picked up, the item disappears, but the ally gains the benefit permanently.

Q - Backtrack Jansen shoots out a wide cone of energy that either destabilizes or re-stabilizes the timeline. Enemies hit by this are slowed by 10/15/20/30% on hit. If used on an ally, any current "slow" status effect is reduced by the same amount.

W - Wibbly-Wobbly Ball Passive: Jansen's base speed is increased by 2/4/6/10% when this ability IS on cooldown.

Active: Jansen pushes out a floating ball of energy that lasts for 15 seconds, or until picked up by an allied champion. Allies who touch this orb have .5/.9/1.2/1.5 seconds restored to all their cooldowns. Orb is consumed upon first touch.

E - Tesseract

Jansen folds time in on itself around himself or an ally, making a shield that absorbs 30/50/90/120(+5% AP). After five seconds, or on recast, the shield detonates, slowing nearby enemies by 15/25/35/45% for 1.5 seconds.

R - Do-Over

After channeling for 2 seconds, Jansen reduces the cooldowns of all allied champions by 20/40/80% and gives them a 10/20/30% Attack Speed boost for five seconds.

Lore:

While I'm still working on it, the basic concept is that when Zilean and Ekko began their experiments with time, they wreaked unknown havoc. The timelines they altered, the realities they shattered, didn't simply disappear like they never existed. They were consumed. Jansen managed to escape by finding a memento of his former life, one that wasn't in the field of influence of their time manipulation.

Jansen wishes the chronomages to see what they have wrought, and to undo the eradication of his home, which was removed from our reality by their influence.