Is the cave-player completely free in tile placement?
The only rule that comes to my mind right now is that If the Cave has any Crystal tiles in its hand during its turn, it must place them before placing any other tiles.
In our last game the cave have placed the tiles always with the edges in the middle so the movement for the knight most of the time was blocked by a wall in the dungeon.
The Knight decides how to turn the Cave Tiles as she reveals them. The rule is that if she entered the tile through an open edge, then she must place an open edge on the side she entered from. If, instead, she entered the tile using e.g. a Map or a Bomb, then she could turn the tile any which way she wants.