You need to reach district 6, level up to level 10 and light up 10 torches in one playthrough. The levels are randomly generated so some levels could be harder/easier than others.
Just find the door to the next district and on the way you should be able to light up 10 torches and gain enough XP to reach level 10.
For more tips and to see me do this check out my video below
See me collect some torches at 2:05