NPC等级是跟着你主基地和你等级走的

官方论坛的。 我英语太烂 不翻译了。主要看最后句
How does NPC Matchmaking work?
You get new NPC opponents, referred to as Blackguard bases in game, when exploring the map and as occasional invasions on your map. Your opponents are selected by a matchmaking process that attempts to give you the right level of challenge. Unlike your Player Matchmaking, your NPC Matchmaking score does NOT decrease. As you defeat the NPC bases, increasingly more difficult ones will spawn.