Jarvan IV

Strengths

You can use the Dragon Strike / Demacian Standard combo to get out of your own Cataclysm arenas.
Split your basic attacks on different champions at the beginning of fights to maximize damage.
Use Demacian Standard as a scouting tool when worried about incoming enemies.

Passive · Martial Cadence — Jarvan's first basic attack on an enemy deals bonus physical damage based on their current Health. This effect cannot occur again on the same enemy for a few seconds.
Q · Dragon Strike — Jarvan IV extends his lance, dealing physical damage and lowering the Armor of enemies in its path. Additionally, this will pull Jarvan to his Demacian Standard, knocking up enemies in his path.
W · Golden Aegis — Jarvan IV calls upon the ancient kings of Demacia to shield him from harm and slow surrounding enemies.
E · Demacian Standard — Jarvan IV carries the pride of Demacia, passively granting him bonus Attack Speed. Activating Demacian Standard allows Jarvan IV to place a Demacian flag that deals magic damage on impact and grants Attack Speed to nearby allied champions.
Ultimate · Cataclysm — Jarvan IV heroically leaps into battle at a target with such force that he terraforms the surrounding area to create an arena around them. Nearby enemies are damaged at the moment of impact.

A suggested 5-lane lineup built around Jarvan IV, based on hero partnerships and role synergy — not win rate.