Here is an example of many of the new abilities that you know see on new champions or reworked champions.
Irelia's next basic attack an enemy champion makes them vulnerable for 3 seconds, increasing all damage they take by 20%. In addition, Irelia gains a shield for 50 (+ 0.25 AD) that stuns nearby champions for 1 second that target Irelia. Enemey champions who are stunned also have their healing reduced by 50% and bleed for 10 + 0.10 AD. If Irelia hits an enemy champion, all of her abilites cooldown are refunded and she gains 20% attack speed for 3 seconds, increasing to 6 seconds if she takes damage during that time.
Passive: Deadly Birds
If Swain has not taken any damage in the last 10 seconds, he becomes immune to all forms of CC for 5 seconds upon taking any damage. Additionally, his basic attacks send deadly birds at the target location, dealing 40 bonus magic damage, and slowing targets by 15% for 2 seconds. Allied champions who hit the slowed champions grant Swain 50 decaying movement speed for 2 seconds. Swain also gets the ability to fly around for 3 seconds, taunting any enemies he touches for 2 seconds (increased to 4 seconds if he takes any damage during this time). Swain also passively regenerates all of his HP if he gets an assist. And gains 100 mana if he gets a kill. And 50 AP (+ 0.25 AP) per every champion he stuns before they die.