- If you don't have "Battle of Chibi (coallition forces)" in free mode you have to get the event.
How to get the battle in empires mode :
Player is not Sun Quan, Hwang Gai, Zhuge Liang or Cao Cao.
Player is in Cao Cao or Sun Quan or Liu Bei faction. Cao Cao faction and Sun Quan + Liu Bei event are different so have to play twice to see both event.
Hwang Gai must be in Sun Quan faction, Zhuge Liang in Liu Bei faction.
Cao Cao must be controling Xiangyang, Sun Quan controls Hefei + one or more area.
Cao Cao and Sun Quan is not allied.
Liu Bei and Cao Cao is not allied.
9+ turns have passed.
Not happen in the month of War Council.
Source: https://psteamcommunity.yuanyoumao.com/app/322520/discussions/0/617329150711428134/
Make sure you are in Liu Bei faction.
And the Player Character is NOT Zhuge Liang.

- After you do the first step correctly, join the battle.
In the battle, help Zhuge Liang by capturing the base that he wants (or the altar), then escort him to the captured base (or the altar). Defend him because some enemies will try to defeat him. After he arrives to the altar, he will begin praying, defend him again. after he done praying, you will get this achievement.