not a novel reader so everything is based on my read of the manhua so far. i think she just wants to live freely. like she mentioned how leilas are all selfish and self serving and once they don’t have a common enemy they all turned on her to drag her down from the position of power bc they covet it. honestly as much as she thought it was a bother and that penelope was an ant to squash i think she genuinely enjoys seeing people squirm and suffer and that’s why she delights in the destruction. i’m guessing why she’s keeping derek hostage is bc he’s more amusing as a toy alive than he is dead. i think her sole focus is just to destroy everything penelope holds dear (which means in the worst timeline once she does succeed her life will be so hollow and meaningless) bc seeing that expression on penelope’s face must thrill her
think of Leila as a plague, altho, a plague that enjoy what it does, destroy lives, and Leila's kin suck out the lives of humans for power and for sustenance
i have read the novel, i don't remember Leila talking about her freeing her kin and then that they try to take over her throne, it's probably just added here in the webtoon, in the novel, everything always restart when her kin was freed, the only time they managed to destroy the world was on the 1st timeline and that's why Vinter used the forbidden magic to turn back time caging them all in a loop
i could be wrong, but maybe the artist or author just want to add some character to Lelia? i don't know, she's already a perfect villain for being irredeemable

so based on the recent chapter, the thing possessing yvonne is leila, but is leila now acting by herself now instead of ‘freeing’ her people like she originally did in previous timelines? like what exactly is her goal, is it just to destroy the world orrr