On the paper that Luan had handed them there was a contract of loyalty and secrecy. Yes, Luan said he could trust these people when he asked Elias to go after them, but it wasn't like he would trust them 100%. If he wanted 100% confidence, something like this was needed.
In the contract, he had written that the moment something Luan had told them and given them express warning that it shouldn't be leaked, the person who signed the contract would be killed if they so much as tried to leak the information. It seemed like a lie since there would probably be no way to find out that they had leaked information.
