Okay, I had a personal philosophy that Dark Type pokemon are like Anti-psychic types that use the negative energies of their mind to inact their abilities, thus why I believe Telepathy wasn't out of their grasp. I alaso believe that Yveltal, being the physical representation of death, has a connection to every living thing, as every can die at one point or another. I probably should have mentioned this earlier, and I apologize for not doing so, but since no one seemed to question it, I didn't see the need. Plus their has been evidence of non-psychic legendaries using telepathy in canon, prime example being Enti.