What is Rek'Sai's motivation?
Disclaimer: I am only paying attention to the old lore for this thread. Please don't go off topic with the lore retcon nonsense.
The first Void Champ, Cho'Gath, is "imprisoned" by summoners. He lets himself stay imprisoned in his cardboard box of a cell until he gets bored. As for the youngest of the Voidborn, Kog'Maw, he is focused entirely on eating everything. His sense of taste is his method to experience the overwhelmingly, delicious environment. Kha'Zix wants to consume worthy prey and adapt their features to become the ultimate life-form. The death of Rengar will be a major step in the Voidreaver's evolutionary meal plan. As for the Void's Knowledge seeker, Vel'Koz, he Learn Beams any interesting pieces of knowledge to analyze and remember. Through this method, he desires to discover Zilean's chronokinetic secrets. Since Rek'sai existed in Runeterra since the era of Ancient Shurima, which means that she was one of the earliest known Voidborn in Runeterra. With this in mind, what drives her?