In the castle, Lucas was with Roderick and the others when he began to feel strange. He felt emotions that weren't his, very subtle but they were present ranging from fear to panic and worry. He knew right then that Magdalene was alive. Not that he doubted before, but he knew she was right amongst the living. He couldn't bring himself to sit back while she was left all alone.
He knew what was happening outside the castle gates, the large numbers of soldiers, witches and evil beings struggling to crawl into the castle. He knew that it was only a matter time before they found their way around it. The soldiers in the castle were fully prepared but they needed something else. Even if the whole team went out they'll be killed and subdued very easily as Eugene's soldiers weren't very easy to kill. They needed Magdalene to undo the spell.
"Sire" Roderick tried to stop him as he abruptly sprung up to leave.
"Speak!" Lucas ordered clearly annoyed.