The exact beginnings of the Second Era are unclear.
EITHER this era began with Xurhuan Zhi / Elysia's separation into the four Dragon Lords / Laiwang, and the Elysian Church's related fracturing.
It's unclear which preceded/caused the other.
OR this era began with Humans and Elves coming into existence.
Either way, the Second Era was distinct from the First mainly by the two races shaped by Gurang Zhi / Solane and Huran Zhi / Nyxal: the Elves and the Humans. These two races flourished in Plumamentia; slowly dominating the many other races under Xurhuan Zhi / Elysia's protection.
This era came to a close once the cult Azurites murdered and subsumed Ulong Lai / Summer and Summer's Domain. Manipulating the Azurites and the Ichor they now possessed, Yuuwu Juriin / Abaddon worked to further their goals.
Gurang Zhi / Solane, concerned for what Ulong Lai / Summer's absence might mean for the Mortal Realm, attempts to bargain with the God Yuuwu Juriin / Abaddon. Huran Zhi / Nyxal, horrified at Gurang Zhi / Solane's misstep, declared him Persona Non Grata and declares a Second Divine War - as well as the onset of a Third Era.