Eren is in frot of Pieck, and the assasin of Sasha, but now, she's telling him that she wants to join his cause, but he doesn't believe her, it's too convenient, he needs more than merely words. He needs proof that she's actually wanting to join his cause, she needs a test, and he knows what to ask her to see just how willing she actually is at: A show of loyalty by Albhen-144 - Hades483.