Full details have been revealed for Kayn, League's new champion, and he kicks ass
His name is Kayn, the shadow reaper, and he is nothing short of badass.
He's an assassin that practices in shadow magics, just like Zed. He intentionally wields a scythe possessed by a Darkin to take advantage of its unrivaled power—even though the Darkin inside could claim is life. With the demon fueled scythe in hand, he will lead the Order of Shadow to shepherd Ionia into a new age of supremacy. He can either bend the will of the Darkin scythe to his will, or it will overcome him, take over his body, and bring ruin to all of Runeterra.
The player can choose to let him evolve into the full-power Shadow Assassin or they can choose to let Rhaast, the Darkin in the scythe, take over, turning him into the Darkin itself. The Shadow Assassin path is an assassin that excels at dealing damage to the back line full of ranged attackers. The Darkin form turns him into a self-sustained bruiser with tons of crowd control. Killing ranged opponents will charge his Shadow transformation, and killing melee champions charges the other, allowing him to reach either transformation faster.
Q - Reaping Slash
Kayn dashes forward and then slashes, dealing physical damage both with the dash and the slash, and it deals bonus damage to monsters. Kain is going to excel as a jungler, and with this gap closer for ganks and bonus damage to monsters, it will make him that much scarier when he meanders into your lane. In Darkin form, it deals bonus percent health damage.
W - Blade's Reach
Another great ganking tool, Kayn's W slows targets by a significant amount in a line in front of him. In Shadow Assassin form, it leaves behind a shadow that casts the ability itself with bonus range. In Darkin form, it knocks up enemies.
E - Shadow Step
Kayn's E grants him a big movement speed boost and allows him to walk through walls. When he walks through the first wall, it will heal him and the duration of the ability will be extended. This will be great for navigating through the enemy jungle and setting traps. In Shadow form, this grants him immunity to slows as well as even more movement speed.
R - Umbral Trespass
Kayn's ultimate allows him to possess any champion he's recently damaged. When he hijacks them, he becomes un-targetable, and he can end the ability early to break free from his host and deal a huge burst of damage. In Shadow form, it can be cast from further away and it resets the bonus damage on his passive. In Darkin form, it deals a large percentage of the target's total health and heals Rhaast in the process.
Kayne is very slippery, very mobile, and very scary. He has high damage and great tools for ganking as well as silently moving from lane to lane and camp to camp. With his high mobility and burst damage, he would also work well as a top or mid laner, depending on which transformation he chooses. Damaging and killing champions gets him closer to transformation in either way though, and jungling would allow him to get to enemy champions easier than any other role.