Can you give me more detail, like what time do you go to the plain, how your game processes, and have you enter to the dungeon at the plain yet?
According to Orc's War Event logs, first, you need to talk with Orgram to start the event.
After that, you need to go to Plains of Death. Please make sure you be there during daytime (6.00 - 19.59).
Then, select "Path to the shine." It should automatically trigger the event which lead you to fight the red orc.
