[Eraqus's eyes widen when Pinkie opens the box to reveal it is empty. Magical artifacts that are important to the safety of this world, now missing? This can't mean anything good.]

It looks like your elements have been replaced with a riddle. [And he can't tell if she's being sarcastic or not...] Does it make any sense to you?

...We should let others know about this. [He figures that the pony princesses at least would want to know.]