Underground Sea map no nameless seer?

I've been running the past 4 days underground sea map to manage and scry the divine beauty and haven't got a single seer.
What is weird is that I clear every corner of map and at the end it still says that there are monsters left from 2-28 monster!

The only advice I can give you is get as much packsize as possible, make them 8-mod corrupted with 20 qual and run every single modifier effect node on the atlas, I did that+ambush on burial chambers and after 2 days and about 100+ maps he spawned. He's exactly the same as reflecting mist, any monster you kill can spawn him so just add as many monsters as possible, and strongboxes being openable again(or having guarded by a stream of monsters) helps a lot with that. And I guess if your build can handle it you can always add a mirror of delirium with the endless delirium fog keystone/slap on a deli orb for more monsters. And don't forget all the small 5% packsize nodes for your influence of choice, that helps a lot. You can usually get an 8-mod map to around 70% packsize with modifier effect, maybe more if you use cartography scarabs of risk.