While none of the champions in League of Legends can be classed as pure antagonists, Cassiopeia was the main antagonist in Shurima: Descent into the Tomb and a semi-antagonist in Rise of Shurima.


Before her transformation into the half-snake half-human she is now, Cassiopeia was a temptress noblewoman working under her family. The Du Coteau family were a wealthy family. Cassiopeia, in a market at the edge of the desert, Cassiopeia sought a guide, Sivir, to take her to the ancient Shuriman empire.

After five days of searching the Shuriman heat, the two find a tower "juddering upwards and a stairway leading underground" and the descend.

Ancient treasures are what await them beneath the tomb, they head deeper, Sivir's men are reckless and are slaughtered by traps within the tomb, Sivir is horrified, but Cassiopeia isn't. She sees a "statue of a serpent silently guarding the door to to the tomb of the Emporers" and smiles, grabbing Sivir's blade and stabbing her in the back, she places her weapon, a key to the door, but is stopped, as the statue of the serpent comes alive and impales her in its jaws. When she comes to, she has become a half human, half-snake woman, cursed by the Shuriman tomb.