Headscratchers / A Plague Tale: Innocence

• What is the Meat Moss made out of? it's partially bodies, but what's the black stuff? How does it get everywhere and make walls?
  • At the cathedral the monks talk about how the rats use human remains to construct their nests. Watch the scene here.
• At the Roman Bath, Lucas brews the elixir for Hugo which as a side effect calms down the rats in their presence. Why didn't they use this elixir to control the rats at Chateau d'Ombrage later on?
  • Presumably, as Hugo was actually directing the rats at that point, his influence trumps magic potion. And didn't they say Hugo drank all the potion, "drink it all in one gulp" or something like that?
  • The rats are somehow part of a supernatural force. That elixir has significance to that force so, once it's been successfully brewed, the rats will not stand in its way. But then once it's been used all bets are off.