[archaeolept]

Trumanator, the game itself says that crumble causes 150 pts of damage to walls. There is no need to tell anyone a publicly known fact, easily checked by right-clicking on a fort. The dark citadel has 600 defense. Thus, 4 crumbles are needed, unless you know the spell is bugged. Also, only 4 if there is no defense, and rlyeh had moved out his remaining troops the turn before. For crumble to work you still need more pts sieging than defending, so 4 is exactly sufficient if you are aware that the defense has run away.

there are many ways to test whether a province has a dome. But, the simplest answer is that domes are shown in the battle screen, so it would have been evident the turn before when WL laid siege, even if he hadn't bothered to previously check. There was no need for anyone telling anyone anything as far as that goes. It is a red herring, afaict.