The male protagonist is a constable returned home his wife and the child in his belly were immortal fighting mana spills over into the pool of extinction himself was taken by a mysterious object into another It's "Immortal Prison", by Cooking Coffee

The Immortal Prison Pagoda, a very strange carry-on prison.

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True Immortals who defy all beings, I know what your cold hearts yearn for.

So I have sought out a good place for you, better than the immortal realm.

There you will have true immortality,

for there, without my permission,

you cannot die if you want to.