"You're going to be extra hands." Loki gestured at the staff, which he set between them, then retrieved the bowl and set it between them as well, close to his left side. "I'm going to cut my left hand and bleed into the bowl, then write with my right. Once I start, I can't stop until it's done, so if the staff needs to be turned or held in place, that's you. If the wound on my hand closes up, that's you, too." Here he pointed at the dagger, resting unobtrusively on a towel nearby.

Then, even though he was moderately sure Thor didn't care about the thought process, he added, "Mountain ash used to be Odin's - Father's - tree." It almost stuck in his throat to name Odin so, still, but it would please Thor and avoid an argument. "The dagger was a gift from Mother a long time ago. So your help is important on a symbolic level, not just practical." He hadn't been lying or flattering when he'd said Thor was the best option.