A Pit Lord champion similar from Heroes of Might and Magic (V and VI). (God I love these Inferno creatures, and their Vorpal Sword.)
If angelic race like Kayle and Morgana exist, why not a demonic champion?
The name Mordred is based from Arthurian Legend, where Mordred is the final foe for King Arthur "Pendragon", his uncle/father. Mordred dies, but he manages to deliver a fatal blow to King Arthur, who dies as well.
In LoL story (fan-fiction), before the rebellion, Morgana had a child, unknown to everyone. But their leader known as "Pendragon, the Redeemer", decided to gather up babies including Mordred, after hearing a prophecy from the Fates he reclaimed, a child born to the day so called "evil" were banished from their homeland, as Mordred was one of them, will destroy Pendragon. Pendragon, along with his angelic warriors took babies into a ship, to crash outside of their homeland. Morgana distraught for the loss of Mordred, went insane and saw her kin and their act of justice as tyranny. However, no one knew that Mordred survived the shipwreck, which landed in the land of opposite race, where demonic beings lives.
What he did from there, only Mordred knows...
Imagine a war in heaven between Mordred and Pendragon, with this music:
(Passive): Mordred increases his armor and magic resist.
(Active): Mordred fold his hellish wing to block one incoming attack more than 35 damage or spell for 2 seconds.
If blocked successfully from a target, the target will gain 3 stacks of "hatred" from Mordred and will be revealed for 5 second, while Mordred gain access to use one of his three new abilities within 2 seconds, with no mana cost.
He can only use one of these abilites from a successful block:
(Q) - Brimstone Divider
(W) - Unforgiving
(E) - Hellraiser
Other primary abilities will used later, after these abilities have been used.
(Active): Mordred leash his target for 6 seconds, forcing the target to only attack Mordred and not his team. Enemies attacking Mordred while he's leashing his target, will deal 20% of damage to the target as well.
If the target breaks the leash, he/she will take magic damage and is revealed, forcing Mordred to use new refreshed abilities on his target with no cost.
If target dies through broken leash, Dreadful Bond is refreshed.