You cannot. You can wait for the flat to naturally elevate as the server cycles otherwise the NPC is based on the level of flat you obtain it as...
Flat 1 = NPC 1
Flat level 10 = NPC 10
so on...
Chat with our AI personalities
It turns to NPC of the same level of the flat you built it on.
Farming a Level 10NPC of Evony Age 2 can be determined through trial and error or through the use of what is commonly called a cheat code. Cheat codes are considered unethical.
Attack it with 100k archers then plunder with 5k archers and warriors
Build troops or attack npc
450 ballista's, 400 transporters. Need 60+ attack to make sure no losses.