Hello xKiriyux,
"Eremes's Ep.1 Culvert" is definetely hard but as always: practice makes perfect!
You can watch this video here submitted by a player so you can have a more clear idea of how the skills function. Make sure to be very careful when the Purple Warning message pops out, you will have to press the Dodge skill right after or you are going to die instantly. The Purple Warning will appear twice when the Boss has around 30% and 10% HP left circa (I am not very sure about the exact amount of HP left ).
I am sure that once you have practiced a bit, you will become a true professional "Golden Thiefbug Slayer"!
See you in game!