Question about the meaning of some words!

[enyacat]

1.He got himself captured, along with how many others, and failed to retrieve the prophecy into the bargain. --What does " into the bargain", especially "bargain" here mean? Why did the author use "how many" instead of "many"?
2.She quieted a little; slopping wine down herself, she took a shaky sip. --What does slop here mean? I don' think it means "guzzle" here, because there's the word sip followed.

The sentences are from "Harry Potter"

Thank you!

[eworthy]

'along with how many others' means we don't know it could be zero or many.
'into the bargain' When bargaining you are offering and asking until a deal is struck. Sometimes, to make the deal you accept something you don't want or give up something you do. In this case 'the bargain' was all that occurred and something that was wanted was not achieved.
"slopping" equals spilling.

[enyacat]

Thank you for your detailed explanation!