Similar to The Injured Pokémon Thread...
Ghetsis mentions several times that Alder had lost one of his partners to illness. I find that this venture into death of Pokémon partners is an interesting direction the games are taking.
Me, like the inquisitive person that I am, would really like to know what Pokémon of Alder's died. Maybe it was his starter that he had had forever like when he set off from his hometown like an maybe an Emboar, Serperior, or Samurott, or maybe it was something else. Maybe he didn't even grow up in the Unova region? Who knows (yet)?
I would really like to get the rest of the forum's take on this subject as this might be explained in the third version, so please, speculate! :D