Give an existing champion a brand new kit and role but with the exact same ability names!
I'll start!
Malzahar, the Prophet of the Void. Class: Tank, Warden!
P, Void Shift: If Malzahar continuously moves towards the same allied or enemy champion for X seconds, he can click them again to blink an additional short distance towards them.
Q, Call of the Void: Malzahar channels for a few seconds, Taunting and Slowing enemies in target direction if they face him.
W, Void Swarm: For a few seconds Malzahar is surrounded with a swarm, negating a portion of all damage he or allies within takes and dealing a portion of the damage around him when the duration ends.
E, Malefic Visions: Malzahar curses target area, causing enemies Nearsight and Visions for a duration. After a moment of only Nearsight, Visions causes allies and enemies outside the Nearsight radius to become semi-visible but appearing as illusions, showing no health and otherwise being indistinguishable from each other.
R, Nether Grasp: Malzahar chants, causing the allied or enemy champion closest to him after a few seconds to be pulled into the void, going into stasis for a short time.