Blade Queen Lissandra
975 RP until June 2nd, normally 1350 RP
From the official announcement:
"Kneel before Blade Queen Lissandra. A mechanical claw erupts at her ironclad feet, tearing through the dirt towards the rebels cowering before her. Those fortunate enough to survive her onslaught find their solace cut short as Lissandra teleports into their midst, beautiful and terrible in all her glory. Dread consumes them. Pieces of metal manifest around the Blade Queen, encasing her in an iron maiden as cruel blades rip through the earth. The screams of pain are quickly silenced; just like that, the rebellion is over as quickly as it began.
Rule the Rift with Blade Queen Lissandra, available now in the League of Legends store for 1350 RP(discounted to 975 RP through June 2)."