Talk to Horus in Khufu Desert Depths.
You must reach LV85 to receive the next scenario quest.

Show Quest Info

Introduction

Horus admitted that originally he had lost all hope in humanity. He had been using the Gold Libra to collect bodies and harvest the souls to maintain his power. The fact that you passed his test has made him see the error of his ways and it has rekindled his hope in humanity. In an attempt to defeat Horus, Set stole Wraith Tome from the netherworld and started a war between the Serra and Berni tribes. Horus is asking you to help him put an end to Set and his war.

Quest Completion

So, what do you say, human? Will you join me so
that we can put an end to the war and finally rid
ourselves of Set?