The one who had sent out the message to Leo was none other than Xander from the tenth. He didn't know what situation Leo would be in, but it was an urgent matter to contact the others. Since they weren't fully aware about who might be around the Blind Swordsman, the content of the message had been vague enough to not leak any secrets or the family's identity.
Paul had ordered Xander to consistently check if the communication channels might open up, and eventually, seemingly out of nowhere, they started to work. The oddest thing was that it had happened in the midst of the attack from the Dalki and the masked forces.
Nonetheless, Xander immediately informed Paul about this discovery. Due to the situation at the tenth castle being far better than anywhere else, the Vampire knight had been able to simply give out commands without having to go in personally. Once notified, he immediately headed back inside the castle to safely talk to the others.