Ancient evil

Be aware of old stuff being able to return. There can always be a case, even if you don't guess it.
It might not be like the first time, or the previous time when you had an encounter with it, but still you'll be faced with things you are somewhat familiar with and you might think that you exactly know where this road is going to get you at.
A big fail - be ready for surprises and be ready to take on things that you haven't seen before. Also, be ready for detours and for temptations and twists.