The last few pages of "Nether Chronicles" actually describe the art of bartending.
The Nether House only stipulates that any being entering must choose a bottle of wine to drink, but doesn't say you can only drink one bottle.
The reason for the saying that drinking two kinds of wine leads to certain death is because the Demon Spirit Wines contain different attributes of Demon Spirit Essence, and drinking two wines will inevitably cause a conflict in attributes, causing great harm to the body.
However, if several Demon Spirit Wines with different attributes are mixed together to achieve balance or mutual restraint, then drinking several or more wines wouldn't be an issue.
Of course, drinking too much is not advisable because some Demon Spirit Wines contain Demon Spirit Essence that is simply too powerful, and a single drop could be lethal.
Not to mention a human body, even the body of a demon cannot withstand it.
