It says that one of his pokemon died years ago becuase a sickness what kind of pokemon was it
After looking at multiple different sites many people including myself believe it is a Volcarona, and I understand that he does have one in his team, but given Alders association with "rebirth" this pokemon could be a reincarnation of his lost pokemon because it does mention that he travels to Relic Castle where you can find a Volcarona. Another reason it could be Volcarona is half his team is bug type so you could say he favors bug type but there is no way at this time to be completely sure what pokemon of his died.
