Trolls everywhere, huge beasts capable of smelling Gremory for quite some distance delayed the whole process of investigation in the walls.
If that wasn't bad enough, the glyphs inscribed on the walls were not as clear as before. Gremory was coming to one wall, noting everything he could in his book before some Troll come close enough and them running to the other wall to gather enough information for each riddle.
Dozens of walls, dozens of riddles. Every one of them was easy things about the world but some of them were leading only to traps. Gremory needed to be sure before following the direction of one wall as if each wall claimed to be the right one while pointing in some direction.
However.
That was not the case, in each riddle, there was also a trigger answer that nullified that answer of the other ones leading only to traps. So, to complete map the changes on the dungeon he needed to know what wall was telling the truth.