Just when the espers and General Leo make peace in Thamasa, Kefka shows up to wreak havoc.
He kills espers to turn them into magicite, becoming more powerful, then kills General Leo.
Despite the espers in the Esper World re-opening the gate to save their friends, Kefka is able to turn them into magicite as well.
When the party regroups on the airship, they discover Emperor Gestahl and Kefka have entered the Esper World, control the Warring Triad statues who created espers millennia ago before turning themselves into stone to create peace, and caused the whole continent that the Esper World was on to float.
Now the party must put an end to the Empire's motives.
Needless to say, a lot happened last time.