riddle - See me once, See me Twice #7

Here I am again, with another See me once riddle. Have fun!

See me once, at the start of the week
See me twice, the men becoming bleak

See me once, when gambling on chinese ground
See me twice, saved but lost time I found

First Hint:

See me once, my dice are divine my friend

See me twice, my brother's story would never end

_{Here are the previous riddles in this series (the solutions there have nothing to do with this one, only the process of getting there).
#1, #2, #3, #4, #5, #6}

Answer

See me once, at the start of the week, when gambling on Chinese ground, my dice are divine.

Mo - may be short for Monday.
mo - the ISO code and Internet country code top-level domain for Macau.
Mo - Tibetan divination which uses dice.

See me twice, the men becoming bleak, saved lost time I found, my brother's story would never end.

This suggests the novel Momo, also know as The Grey Gentlemen, by Michael Ende. Momo is a girl who saves her society from the sinsister Men in Grey who are stealing the time of humans.
Michael Ende also wrote The Neverending Story, centred on the boy Bastian Balthazar Bux.