Every round the challenge gave us 3 different elements in the same format:
	'NEHQAOBYXUGDZMPSKFRIJVWLCT', 2, 'VUB QBJV CHN VK BSVBI KWI QWJGSBJJ GJ VK QB QKIS GSVK GV'
The first element (NEHQAOBYXUGDZMPSKFRIJVWLCT) is always a 26 chars string, a strong indicator of a substitution alphabet. The second element (2) is always a number between 1 and 26, which seems like an offset. It could be related to a rotation, like in a Caesar Cipher. The last element is probably the encrypted message itself.
With these informations in mind we confirmed there were indeed both a substitution and a rotation involved. To decrypt, we first substituted back the message according to the alphabet, and then applied a rotation according to the offset.
The script in the link gave us what we needed.