[quote=@Balthazar007]
I see what you mean, but let me clear something up there. It wasn't mentioned anywhere directly, but items from the Pokemon World don't work when you first arrive in Earth. 

Sycamore arrived a year ago, in this RP (when the Gen 6 Pokemon were introduced). That can also be when your character was brought over. From there they had to reverse engineer items from the Pokemon world so they would be compatible on Earth. In this case, let's say it took six months to get Key Stones working. 

Therefore your character could have gotten a Key Stone about six months ago. 
[/quote]
That works even better for his plot. I'm thinking that Winter was relatively knowledgeable about Mega Evolution in the Pokémon world, but knows virtually nothing about how it works on Earth. This could also explain why he can only Mega Evolve his Absol. As it were, I'm thinking that Gallade, while having the stone, doesn't meet the requirements to Mega Evolve (ex: lacks a strong bond with its trainer, Earth somehow affects this, etc). I can also remove the Galladite all together (since they're rare), I just thought that it made a bit sense for someone researching the topic to have more than one Mega Stone. I'll be sure to mention that he's only had the Key Stone for about six months in his biography though.