deal with the wrong demon [cuphead and Bendt]

What happened to mughead and cuphead in past

-this is past-
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Cuphead and Mughead made a gambling with the demon king. Whoever loses has to give one soul, and whoever wins will decide which soul they wanted to take. Cuphead and Mughead had no chance of winning toward the demon king......

They lost in gambling. The demon king won. The demon king wanted to take Mugheads soul Cuphead refused but he can't do anything at all expect just staring his brothers soul getting taken away from His own body. The demon king smiled in red burning eyes and said "Who is going to win in this gambling was obvious in the start."
After hearing that words from The demon king Cuphead wanted his brother back so badly.

 
very short